Sword of Spirit
Legend
Reverse Engineering the Real Rules of Attunement
This post is an in-depth examination of why Magic Item A requires attunement, while apparently similar Magic Item B does not. While my opinions about some of the design decisions will no doubt show through, I'm intending this post to present my findings about the proposed real rules behind attunement assignment, not my evaluation regarding the appropriateness of the design decisions leading to those rules.
There are, unsurprisingly, limitations to this analysis. While I believe the top level principles drawn out are reliable, uncertainty is present in some of the details. This is primarily because we cannot always tell whether a correlation is causal or coincidental. For example, just because it is true that every item with feature X requires attunement, and every item without feature X does not require attunement, it doesn't necessarily mean that the presence of that feature is the causal factor. Where possible I have attempted to control for those variables, such as by comparing items that have only one feature each. After deriving the principles that can be derived in that manner, however, there were enough remaining patterns that I feel it was justified to attempt to extract other rules, even at risk of error. It is likely that some of the rules that I have discovered (especially the ones further down the list) are in fact coincidences based on either arbitrary design or some other rule I have not yet been able to identify despite way too much time spent on this.
In spite of those limitations, I believe the majority of the rules were probably applied in some form (consciously or unconsciously) by the designers, and that the remaining ones help demonstrate certain principles involved in the design.
I have restricted the analysis to magic items in the Dungeon Master's Guide. This eliminates design consistency/quality issues that may be introduced by including every magic item in every official adventure. On a later topic I will include some additional insight I derived by examining magic items from Xanathar's Guide to Everything and Tasha's Cauldron of Everything.
Sentient magic items and artifacts have been excluded from the analysis, as they all require attunement, and almost certainly should.
I have determined what counts as an individual magic item, for purposes of this analysis, primarily by whether it contains its own entry or meaningful sub-entry in the DMG, or differs within an entry by rarity. So, for instance, a +1 weapon and a +2 weapon are two different items, and each type of figurine of wondrous power is a unique item, but ring of resistance, which varies only by damage type, is a single item. This gives us 341 magic items to analyze.
When Attunement Matters
One important thing to realize when analyzing the functional effects of attunement, is that it will rarely limit how many magic items a character can utilize if using the typical magic item distribution presented in the DMG and XGtE. By 20th level, on average, each character will end up with about 3 items that require attunement--exactly the number allowed. Only if your campaign produces more magical items than the random tables would, and if you get to high enough level for this to matter, or if you are not distributing them amongst the party equally, will you be likely to bump into the 3 item limitation often. What this means is that the 3 item limit principle is designed for campaigns that have more than the expected number of magic items, and I'll address the ramifications of that in a further topic.
Before going into the official principles of assigning attunement and the proposed real rules of it, we should first clear up what are not rules or principles of attunement assignment.
NOT Principles
1. Item Power. Item power in 5e D&D is designated by means of rarity, not by requirement for attunement. An Uncommon item that requires attunement should not therefore be more powerful than one that does not, nor is the rarity level of an item reduced by requiring attunement. Certain trends may make this appear to be so in some situations, but I do not believe that is actually a factor.
2. Item "Interestingness". It should go without saying, but attunement isn't a fun-bat to limit how many interesting items someone should be able to have.
3. Multiple Benefits. There are very few items that provide multiple benefits that do not also require attunement. However, those that are not explained by other--more consistent--principles are very few, and barely more numerous than those that do not require attunement.
The Official Principles
On page 284 of the DMG, we are given the official "rules of thumb" to determine whether a magic item should require attunement.
1. If havingall the characters in a party pass an item around to gain its lasting benefits would be disruptive, the item should require attunement.
2. If the item grants abonus benefit that other items also grant, it's a good idea to require attunement so that characters don't try to collect too many of those items.
The one word change I made to each of those principles is essential to making them functional. While the change to the second principle is just a clarification, the first principle would only apply to a handful of items if it were intended to apply only to items that you'd pass around for the whole group to use in a situation. If you, instead, expand it to include passing items to the best member of the party at any particular time (such as giving the headband of intellect and the sentinel shield to the rogue while they are searching for traps, and then having the wizard and fighter reclaim them before an expected battle) it becomes a principle that actually applies more than once in a blue moon, and might be a reasonable basis for an attunement requirement.
The reason I'm doing this extremely time-consuming analysis, is that those two principles fail to explain the attunement requirement (or lack thereof) for many, many items in the DMG. If you follow those principles in your own magic items design, you will almost certainly end up with items that you do not require attunment for that that game designers would have, and vice versa.
It is clear from my analysis that the principles they told us to follow to derive the kind of results we see fail to produce those results with any sort of reliability. They also require quite a bit of arbitrary decision-making to determine whether or not such principles apply. Unlike in some parts of the game where leaving things flexible so the DM can arbitrarily decide can be a good thing, I can't think of any benefit to it in this situation. (I am assuming that these guideline should be intended to help us make magic items that are similar in attunement requirements to the ones WotC makes, since that seems to me to be what most people would expect and desire out of such guidelines.)
Statistically the official principles (applied as accurately as I could) are about 77% accurate if consumable items are included, or about 72% accurate if you stick to permanent items.
The Real Rules
The proposed rules I will present are about 93% accurate when including consumables, and 91% accurate for permanent items only. In addition, there are significantly fewer judgment calls to be made as to whether a rule applies to an item or not. The vast majority of the time it is obvious.
There are 10 items (9 requiring attunement; 1 not) that can be explained by the official principles but not by these rules. There are 64 items (41 requiring attunement; 23 not) that can be explained by these rules but not by the official principles. There are 13 items (11 requiring attunement; 2 not) that cannot be explained by either the official principles or by these rules.
The Anomalies and Mount Items
Three items break otherwise consistent rules in such a way that it seems best to simply acknowledge them as anomalies. These three items do not require attunement, even though one of the rules should require them to. Two of these items should also require attunement by the official principles.
Adamantine Armor. While it is debatable whether adamantine armor is even a magic item, for purposes of this analysis I chose to take its placement in the list as intentional (maybe there can be armor made of adamantine that isn't magical, but we'll assume that this particular armor is magical in nature). Adamantine armor has a special feature that preserves hit points, and should require attunement, but does not. (This is the only one that the official rules don't call for attunement on.)
Goggles of Night. These provide special vision, and should require attunement, but do not.
Periapt of Proof Against Poison. This provides damage immunity, which definitely should require attunement, but does not.
In addition, none of the three items that are intended for use by mounts (horseshoes of a zephyr, horseshoes of speed, and saddle of the cavalier) require attunement, even though the saddle (and possibly the horseshoes of speed) probably should. Since I believe this was a general decision not to make mounts attune to items I'm treating these anomalies as non-equippable items which do not require attunement. If they knew at the time there would be playable centaurs, they likely wouldn't have automatically exempted horseshoes.
Following the Rules
To analyze any item according to these rules, you can either refer to the table, or follow the step-by step rules below it, whichever method you prefer.
The Table
Identify which category the item belongs to (explained in more detail in Step 2), and then read down the row of features and identify every feature the item possesses (explained in more detail in Steps 1, 3, 4, and 5). If any of those features indicate a Y for that item's category, it requires attunement. If no features indicate a Y, and all features indicate an n, the item does not require attunement. If no features indicate a Y, and at least one feature indicates a ?, these rules cannot determine whether the item requires should require attunement (I'd err on the side of not requiring it if it's an item you are creating). For a more in-depth explanation of the categories and features, see the step-by-step rules below.
Step-By-Step Rules
Step 1: First Degree Requirements
If an item (with the exception of the anomaly above) has any of the following features, it requires attunement; full stop.
-Restricted User: Class, race, alignment, or other
-Cursed
-Attribute Increase/Set: Increases an attribute or automatically sets it to a certain value
-Non-armor AC Bonus: Non-armor provides a bonus to AC or a new way of determining AC
-Damage Resistance or Immunity
-Saving Throw Advantage/Bonus: Advantage on, or a bonus to, any saving throws (even highly situational ones)
-Extra Equipment Slot: Effectively provides an extra equipment slot (such as an ioun stone, dancing sword, or scimitar of speed)
-At-Will, Non Ritual, Leveled Spell: Allows you to cast anything except a cantrip or a ritual spell at-will
If none of those features apply to an item, it may or may not require attunement. Continue to the next step.
Step 2: Categorical Exclusions
If the item falls into any of the following categories, it does not require attunement.
-Consumable: Consumable items refer to items that become useless/non-magical once depleted, and will inevitably be depleted by use, such as potions, scrolls, a chime of opening, a horn of blasting, or a ring of three wishes. Items which retain some benefit even after their charges are depleted, like a luck blade, or a nine lives stealer are not considered consumables. Items which only risk depletion by wielder choice, like wands, staves, or a wind fan are also not considered consumables. (The helm of brilliance is a consumable because even though you can choose not to use all its charges and therefore keep the permanent benefits, it is designed to eventually blow up when you fail a save versus fire damage--which you almost certainly will in any lengthy campaign. Fortunately, it's the only tricky one in the list, and it requires attunement from Step 1, so it's only of interest for completeness.)
-Non-Equippable: Non-equippable items are items that are neither worn like armor, jewelry, or clothing, nor wielded for ongoing usage like a weapon or spellcasting focus. Containers, like bags, haversacks, or quivers are non-equippable, as are items that function regardless of whether they are being carried or attended, like a lantern of revealing. Some non-equippable items must be held to be activated, but either cannot be held after activating them, like a consumable, a folding boat, or a well of many worlds, or provide no ongoing benefit to continuing to hold them, like a wind fan or a horn of valhalla. Items that explicitly provide a benefit by being "on your person" are not considered non-equippable.
-Non-Combat: Non-combat items are items that can only be useful in combat in rare situations with a lot of creativity. This is generally because they take too long to activate in a typical (three round) combat, or because the benefit they provide isn't directly relevant to combat. It is important to note that anything that improves your chances to detect creatures, such as a bonus to Wisdom (Perception), X-Ray vision, or magic detection counts as a combat item.
All other items are Permanent Equippable Combat items and may or may not require attunement. Continue to the next step.
Step 3: Second Degree Requirements
If the item (with the exception of the two anomalies above) has any of the following features, it requires attunement.
-Grants/Improves Vertical Movement: Such as flight, climbing, or jumping
-Light Generation or Special Vision: Includes granting X-Ray Vision, Blindsight, Truesight, etc, as well as simply shedding light
-Effect from Being on Person: Has a stated effect simply by being on your person, such as pipes of the sewers or weapon of warning
-HP Preservation Not From Armor AC Bonus: See below
-Level 6th+ Spell
Hit point preservation means it has a feature other than those already accounted for (AC bonus, save bonus, damage resistance/immunity) which can directly preserve hit points of the wielder or another. These include things like the attack redirection of an arrow-catching shield, and the disadvantage on provoked opportunity attacks of the boots of speed, as well as the more straightforward disadvantage to be attacked from a cloak of displacement, and regeneration from a ring of regeneration.
If none of those features apply to the item, it may or may not require attunement. Continue to the next step.
Step 4: Effect Exclusions
If the only remaining features of the item are from the following list, it does not require attunement.
-Armor Bonus on Armor/Shield
-Attack/Damage Bonus on Weapon
-Ritual Spell: Casts a spell with the ritual tag. (One might assume cantrips would also be excluded, but there are no examples that aren't already covered by a higher rule, so I can't determine that.)
-Water Breathing or Water Movement: Grants water breathing, water walking, a swim speed or bonus to water movement
-Disease Immunity
-Single 1/Day Spell, 5th Level or Less: Would also apply to spells that could be cast less than 1/day.
If the item has features that are not on that list, it may or may not require attunement. Continue to the next step.
Step 5: Rule Adjacency
If any of the remaining features of the item are rules adjacent to an existing attunement-requiring feature, it requires attunement.
Rule adjacent features are those that don't entirely fit into another attunement requirement, but are conceptually adjacent. This is the last (and most speculative) of the rules.
For the items in the DMG, this criterion explains attunement for only 4 items: bracers of archery (the damage boost is rules adjacent to an attribute increase), cloak of invisibility (its usage is pretty close to effectively at-will), ring of evasion (automatic success on a save 3/day is similar to advantage on saves), and ring of free action (not quite as good as at-will freedom of movement, but similar in many ways).
If the item has remaining features that are unaccounted for, it may or may not require attunement. Continue to the final step.
Step 6: Resolution
At this point, these rules have completed their processing and find no reason for a remaining item to require attunement. If you assume such an item does not require attunement, you hit the accuracy levels I indicated for these rules: 93% for all items, or 91% for permanent items.
Conclusion
Those are, as best as I can determine within the acknowledged and explained limits, the real rules of magic item attunement.
Some might question the utility of those proposed rules, given that they are not perfect. In fact someone (smarter than I) could likely derive a convoluted set of rules that could be applied to indicate with 100% accuracy why each item in the DMG requires attunement. Of course, some of the rules would rely on irrelevent details like the length of the item name, or how many times the word "the" appears in the item description, etc. In other words, it wouldn't actually tell us anything.
I believe these rules are useful. These rules refer to actual game-meaningful effects of the items--the sorts of things you might be thinking about when you are deciding whether a new item you have created should require attunement or not. These rules drill down to find out which features appear to have a causal relationship to attunement requirements. These rules focus on meaningful distinctions already known in the 5e system.
In my opinion, these rules, despite their imperfections, simply better explain why the designers did what they did more often than the brief description given in the DMG does.
How Can You Use This?
There are variety of ways this information can be useful.
If you like attunement working as it does, you can use these step-by-step rules to more accurately assign attunement to items you create according to patterns found in the DMG. If you prefer, when you get to Step 6, instead of not requiring attunement for any item that gets that far, you could at that point apply the official rule of thumb principles, which might boost your accuracy even further (for the items in the DMG, switching to those principles at Step 6 gets us to 16 unexplained items instead of 23, increasing the overall accuracy to 95%/94%).
If you, like me, are considering revising the attunement system, you can use it to make more informed choices. You might decide to make a minor tweak, like saying that user requirements shouldn't require attunement. The items just won't activate if you aren't the right class, etc. Or you might decide to entirely rebuild the attunement system, hopefully getting some use out of this material to give you a head start.
You might not have any use for it in your own game, but maybe you could help the rest of us out by pointing out further rules or patterns that I missed, or mistakes that I made.
Where Do We Go From Here?
Sometime in the hopefully near future, I plan to really dissect the effects of how attunement currently works. I plan to come up with some alternative ideas for how to handle it to maintain the concept in the game but refine it to better accomplish desireable goals and not accomplish undesireable ones (currently, attunement does an unfortunately good job of uneccessarily limiting interesting items).
This post is an in-depth examination of why Magic Item A requires attunement, while apparently similar Magic Item B does not. While my opinions about some of the design decisions will no doubt show through, I'm intending this post to present my findings about the proposed real rules behind attunement assignment, not my evaluation regarding the appropriateness of the design decisions leading to those rules.
There are, unsurprisingly, limitations to this analysis. While I believe the top level principles drawn out are reliable, uncertainty is present in some of the details. This is primarily because we cannot always tell whether a correlation is causal or coincidental. For example, just because it is true that every item with feature X requires attunement, and every item without feature X does not require attunement, it doesn't necessarily mean that the presence of that feature is the causal factor. Where possible I have attempted to control for those variables, such as by comparing items that have only one feature each. After deriving the principles that can be derived in that manner, however, there were enough remaining patterns that I feel it was justified to attempt to extract other rules, even at risk of error. It is likely that some of the rules that I have discovered (especially the ones further down the list) are in fact coincidences based on either arbitrary design or some other rule I have not yet been able to identify despite way too much time spent on this.
In spite of those limitations, I believe the majority of the rules were probably applied in some form (consciously or unconsciously) by the designers, and that the remaining ones help demonstrate certain principles involved in the design.
I have restricted the analysis to magic items in the Dungeon Master's Guide. This eliminates design consistency/quality issues that may be introduced by including every magic item in every official adventure. On a later topic I will include some additional insight I derived by examining magic items from Xanathar's Guide to Everything and Tasha's Cauldron of Everything.
Sentient magic items and artifacts have been excluded from the analysis, as they all require attunement, and almost certainly should.
I have determined what counts as an individual magic item, for purposes of this analysis, primarily by whether it contains its own entry or meaningful sub-entry in the DMG, or differs within an entry by rarity. So, for instance, a +1 weapon and a +2 weapon are two different items, and each type of figurine of wondrous power is a unique item, but ring of resistance, which varies only by damage type, is a single item. This gives us 341 magic items to analyze.
When Attunement Matters
One important thing to realize when analyzing the functional effects of attunement, is that it will rarely limit how many magic items a character can utilize if using the typical magic item distribution presented in the DMG and XGtE. By 20th level, on average, each character will end up with about 3 items that require attunement--exactly the number allowed. Only if your campaign produces more magical items than the random tables would, and if you get to high enough level for this to matter, or if you are not distributing them amongst the party equally, will you be likely to bump into the 3 item limitation often. What this means is that the 3 item limit principle is designed for campaigns that have more than the expected number of magic items, and I'll address the ramifications of that in a further topic.
Before going into the official principles of assigning attunement and the proposed real rules of it, we should first clear up what are not rules or principles of attunement assignment.
NOT Principles
1. Item Power. Item power in 5e D&D is designated by means of rarity, not by requirement for attunement. An Uncommon item that requires attunement should not therefore be more powerful than one that does not, nor is the rarity level of an item reduced by requiring attunement. Certain trends may make this appear to be so in some situations, but I do not believe that is actually a factor.
2. Item "Interestingness". It should go without saying, but attunement isn't a fun-bat to limit how many interesting items someone should be able to have.
3. Multiple Benefits. There are very few items that provide multiple benefits that do not also require attunement. However, those that are not explained by other--more consistent--principles are very few, and barely more numerous than those that do not require attunement.
The Official Principles
On page 284 of the DMG, we are given the official "rules of thumb" to determine whether a magic item should require attunement.
1. If having
2. If the item grants a
The one word change I made to each of those principles is essential to making them functional. While the change to the second principle is just a clarification, the first principle would only apply to a handful of items if it were intended to apply only to items that you'd pass around for the whole group to use in a situation. If you, instead, expand it to include passing items to the best member of the party at any particular time (such as giving the headband of intellect and the sentinel shield to the rogue while they are searching for traps, and then having the wizard and fighter reclaim them before an expected battle) it becomes a principle that actually applies more than once in a blue moon, and might be a reasonable basis for an attunement requirement.
The reason I'm doing this extremely time-consuming analysis, is that those two principles fail to explain the attunement requirement (or lack thereof) for many, many items in the DMG. If you follow those principles in your own magic items design, you will almost certainly end up with items that you do not require attunment for that that game designers would have, and vice versa.
It is clear from my analysis that the principles they told us to follow to derive the kind of results we see fail to produce those results with any sort of reliability. They also require quite a bit of arbitrary decision-making to determine whether or not such principles apply. Unlike in some parts of the game where leaving things flexible so the DM can arbitrarily decide can be a good thing, I can't think of any benefit to it in this situation. (I am assuming that these guideline should be intended to help us make magic items that are similar in attunement requirements to the ones WotC makes, since that seems to me to be what most people would expect and desire out of such guidelines.)
Statistically the official principles (applied as accurately as I could) are about 77% accurate if consumable items are included, or about 72% accurate if you stick to permanent items.
The Real Rules
The proposed rules I will present are about 93% accurate when including consumables, and 91% accurate for permanent items only. In addition, there are significantly fewer judgment calls to be made as to whether a rule applies to an item or not. The vast majority of the time it is obvious.
There are 10 items (9 requiring attunement; 1 not) that can be explained by the official principles but not by these rules. There are 64 items (41 requiring attunement; 23 not) that can be explained by these rules but not by the official principles. There are 13 items (11 requiring attunement; 2 not) that cannot be explained by either the official principles or by these rules.
The Anomalies and Mount Items
Three items break otherwise consistent rules in such a way that it seems best to simply acknowledge them as anomalies. These three items do not require attunement, even though one of the rules should require them to. Two of these items should also require attunement by the official principles.
Adamantine Armor. While it is debatable whether adamantine armor is even a magic item, for purposes of this analysis I chose to take its placement in the list as intentional (maybe there can be armor made of adamantine that isn't magical, but we'll assume that this particular armor is magical in nature). Adamantine armor has a special feature that preserves hit points, and should require attunement, but does not. (This is the only one that the official rules don't call for attunement on.)
Goggles of Night. These provide special vision, and should require attunement, but do not.
Periapt of Proof Against Poison. This provides damage immunity, which definitely should require attunement, but does not.
In addition, none of the three items that are intended for use by mounts (horseshoes of a zephyr, horseshoes of speed, and saddle of the cavalier) require attunement, even though the saddle (and possibly the horseshoes of speed) probably should. Since I believe this was a general decision not to make mounts attune to items I'm treating these anomalies as non-equippable items which do not require attunement. If they knew at the time there would be playable centaurs, they likely wouldn't have automatically exempted horseshoes.
Following the Rules
To analyze any item according to these rules, you can either refer to the table, or follow the step-by step rules below it, whichever method you prefer.
The Table
Identify which category the item belongs to (explained in more detail in Step 2), and then read down the row of features and identify every feature the item possesses (explained in more detail in Steps 1, 3, 4, and 5). If any of those features indicate a Y for that item's category, it requires attunement. If no features indicate a Y, and all features indicate an n, the item does not require attunement. If no features indicate a Y, and at least one feature indicates a ?, these rules cannot determine whether the item requires should require attunement (I'd err on the side of not requiring it if it's an item you are creating). For a more in-depth explanation of the categories and features, see the step-by-step rules below.
Step-By-Step Rules
Step 1: First Degree Requirements
If an item (with the exception of the anomaly above) has any of the following features, it requires attunement; full stop.
-Restricted User: Class, race, alignment, or other
-Cursed
-Attribute Increase/Set: Increases an attribute or automatically sets it to a certain value
-Non-armor AC Bonus: Non-armor provides a bonus to AC or a new way of determining AC
-Damage Resistance or Immunity
-Saving Throw Advantage/Bonus: Advantage on, or a bonus to, any saving throws (even highly situational ones)
-Extra Equipment Slot: Effectively provides an extra equipment slot (such as an ioun stone, dancing sword, or scimitar of speed)
-At-Will, Non Ritual, Leveled Spell: Allows you to cast anything except a cantrip or a ritual spell at-will
If none of those features apply to an item, it may or may not require attunement. Continue to the next step.
Step 2: Categorical Exclusions
If the item falls into any of the following categories, it does not require attunement.
-Consumable: Consumable items refer to items that become useless/non-magical once depleted, and will inevitably be depleted by use, such as potions, scrolls, a chime of opening, a horn of blasting, or a ring of three wishes. Items which retain some benefit even after their charges are depleted, like a luck blade, or a nine lives stealer are not considered consumables. Items which only risk depletion by wielder choice, like wands, staves, or a wind fan are also not considered consumables. (The helm of brilliance is a consumable because even though you can choose not to use all its charges and therefore keep the permanent benefits, it is designed to eventually blow up when you fail a save versus fire damage--which you almost certainly will in any lengthy campaign. Fortunately, it's the only tricky one in the list, and it requires attunement from Step 1, so it's only of interest for completeness.)
-Non-Equippable: Non-equippable items are items that are neither worn like armor, jewelry, or clothing, nor wielded for ongoing usage like a weapon or spellcasting focus. Containers, like bags, haversacks, or quivers are non-equippable, as are items that function regardless of whether they are being carried or attended, like a lantern of revealing. Some non-equippable items must be held to be activated, but either cannot be held after activating them, like a consumable, a folding boat, or a well of many worlds, or provide no ongoing benefit to continuing to hold them, like a wind fan or a horn of valhalla. Items that explicitly provide a benefit by being "on your person" are not considered non-equippable.
-Non-Combat: Non-combat items are items that can only be useful in combat in rare situations with a lot of creativity. This is generally because they take too long to activate in a typical (three round) combat, or because the benefit they provide isn't directly relevant to combat. It is important to note that anything that improves your chances to detect creatures, such as a bonus to Wisdom (Perception), X-Ray vision, or magic detection counts as a combat item.
All other items are Permanent Equippable Combat items and may or may not require attunement. Continue to the next step.
Step 3: Second Degree Requirements
If the item (with the exception of the two anomalies above) has any of the following features, it requires attunement.
-Grants/Improves Vertical Movement: Such as flight, climbing, or jumping
-Light Generation or Special Vision: Includes granting X-Ray Vision, Blindsight, Truesight, etc, as well as simply shedding light
-Effect from Being on Person: Has a stated effect simply by being on your person, such as pipes of the sewers or weapon of warning
-HP Preservation Not From Armor AC Bonus: See below
-Level 6th+ Spell
Hit point preservation means it has a feature other than those already accounted for (AC bonus, save bonus, damage resistance/immunity) which can directly preserve hit points of the wielder or another. These include things like the attack redirection of an arrow-catching shield, and the disadvantage on provoked opportunity attacks of the boots of speed, as well as the more straightforward disadvantage to be attacked from a cloak of displacement, and regeneration from a ring of regeneration.
If none of those features apply to the item, it may or may not require attunement. Continue to the next step.
Step 4: Effect Exclusions
If the only remaining features of the item are from the following list, it does not require attunement.
-Armor Bonus on Armor/Shield
-Attack/Damage Bonus on Weapon
-Ritual Spell: Casts a spell with the ritual tag. (One might assume cantrips would also be excluded, but there are no examples that aren't already covered by a higher rule, so I can't determine that.)
-Water Breathing or Water Movement: Grants water breathing, water walking, a swim speed or bonus to water movement
-Disease Immunity
-Single 1/Day Spell, 5th Level or Less: Would also apply to spells that could be cast less than 1/day.
If the item has features that are not on that list, it may or may not require attunement. Continue to the next step.
Step 5: Rule Adjacency
If any of the remaining features of the item are rules adjacent to an existing attunement-requiring feature, it requires attunement.
Rule adjacent features are those that don't entirely fit into another attunement requirement, but are conceptually adjacent. This is the last (and most speculative) of the rules.
For the items in the DMG, this criterion explains attunement for only 4 items: bracers of archery (the damage boost is rules adjacent to an attribute increase), cloak of invisibility (its usage is pretty close to effectively at-will), ring of evasion (automatic success on a save 3/day is similar to advantage on saves), and ring of free action (not quite as good as at-will freedom of movement, but similar in many ways).
If the item has remaining features that are unaccounted for, it may or may not require attunement. Continue to the final step.
Step 6: Resolution
At this point, these rules have completed their processing and find no reason for a remaining item to require attunement. If you assume such an item does not require attunement, you hit the accuracy levels I indicated for these rules: 93% for all items, or 91% for permanent items.
Conclusion
Those are, as best as I can determine within the acknowledged and explained limits, the real rules of magic item attunement.
Some might question the utility of those proposed rules, given that they are not perfect. In fact someone (smarter than I) could likely derive a convoluted set of rules that could be applied to indicate with 100% accuracy why each item in the DMG requires attunement. Of course, some of the rules would rely on irrelevent details like the length of the item name, or how many times the word "the" appears in the item description, etc. In other words, it wouldn't actually tell us anything.
I believe these rules are useful. These rules refer to actual game-meaningful effects of the items--the sorts of things you might be thinking about when you are deciding whether a new item you have created should require attunement or not. These rules drill down to find out which features appear to have a causal relationship to attunement requirements. These rules focus on meaningful distinctions already known in the 5e system.
In my opinion, these rules, despite their imperfections, simply better explain why the designers did what they did more often than the brief description given in the DMG does.
How Can You Use This?
There are variety of ways this information can be useful.
If you like attunement working as it does, you can use these step-by-step rules to more accurately assign attunement to items you create according to patterns found in the DMG. If you prefer, when you get to Step 6, instead of not requiring attunement for any item that gets that far, you could at that point apply the official rule of thumb principles, which might boost your accuracy even further (for the items in the DMG, switching to those principles at Step 6 gets us to 16 unexplained items instead of 23, increasing the overall accuracy to 95%/94%).
If you, like me, are considering revising the attunement system, you can use it to make more informed choices. You might decide to make a minor tweak, like saying that user requirements shouldn't require attunement. The items just won't activate if you aren't the right class, etc. Or you might decide to entirely rebuild the attunement system, hopefully getting some use out of this material to give you a head start.
You might not have any use for it in your own game, but maybe you could help the rest of us out by pointing out further rules or patterns that I missed, or mistakes that I made.
Where Do We Go From Here?
Sometime in the hopefully near future, I plan to really dissect the effects of how attunement currently works. I plan to come up with some alternative ideas for how to handle it to maintain the concept in the game but refine it to better accomplish desireable goals and not accomplish undesireable ones (currently, attunement does an unfortunately good job of uneccessarily limiting interesting items).
