aboyd
Explorer
There is a free D&D 3.5 PDF called The Practical Enchanter. In it there is a system for creating custom curses, starting on page 60. Curses are weaker than normal spells, but they supposedly can be used by non-magical types to strike back against overpowering oppressors. However, the book then goes on to list the curses as spells (which commoners cannot cast)!
I am going to present here a modified version of that curse system which does allow curses to be used by anyone, including PCs & commoners. However, curses default to the Evil descriptor, so paladins generally wouldn't use a curse. Circumstances can change the descriptor, so nothing is written in stone.
If you are able to cast spells, you can use curses as if they were normal spells. Generally, you wouldn't do this, as normal spells are more powerful. However, if you are up against an enemy that is too powerful, this curse system would allow you to issue curses from a safe distance. In addition, with careful application of modifiers, you can cast a curse that is far more difficult for the enemy to remove than a normal "Bestow Curse" spell.
If you are not able to cast spells, you can sacrifice levels in order to cast a curse. If you are a spellcaster but did not chose a curse as one of your daily spells, you may also opt to sacrifice levels to cast a curse. While that may seem like an incredibly unappealing way to create a spell effect, since curses are typically used by people who are desperate or dying, they often don't care about the level loss anymore.
Limitations
You cannot cast a dying curse (using an immediate action to get your curse out before the killing blow lands) if you are flat-footed or otherwise unaware of the impending strike.
Curses are powered by malevolent spirits. If you use a curse in a normal spell slot, you essentially bind a spirit to your cause. In so doing, you need not worry or track what happens next. The spirit will do its work, and you are free to go on your way.
However, if you cannot use spell slots, you end up using your own spiritual force to power the curse. This means you cannot come back to haunt someone as a ghost (or anything else). This means you cannot be brought back to life. Your soul has a prior engagement, so to speak. Of course, if the curse is lifted, then hauntings and new life may be possible (but if you have cast multiple curses this way, all of them must be lifted, first).
Based upon the prior paragraph, you may deduce that it is also impossible for the undead to cast curses, unless they have spell slots. This is because an undead without spell slots would need to commit its soul to the curse, but the soul is already being used to power their undead form! Or in some cases, their undead form is not tied to any soul at all (such as skeletons & zombies), and thus there is no soul available to power such a curse. This limitation should be extended to any creature that does not have a soul, such as a construct.
As an aside, because curses are actually powered by something that has some kind of sentience, you should expect that curses will not be convenient for the cursed. For example, someone cursed to hear voices (affliction curse, page 62) will not get to declare "the voices only happen at night and I sleep through them." Instead, the curse will likely cause the voices to occur at a time when the cursed person really wouldn't appreciate it. Note that whatever these sentient, malevolent spirits are, they are not prescient, so they cannot always time their effects for the most perfectly disruptive moment. They simply execute the curse to the best of their limited abilities.
Step 1
Determine the level cap of the curse you wish to cast. As a spellcaster, a curse can fill any slot you have open, but no more. Curses work just like spells for you, with DCs calculated as is normal for your class. You can move on to step 2.
If you do not have slots open (or are not a spellcaster), you default to your charisma modifier as your maximum spell level. Since curses can be negative levels, it's still possible for someone with a terrible charisma score to cast a curse (for example, a character with a charisma of 6 could cast up to a level -2 curse). Note that this limitation applies to the calculated curse level (step 3), not the base curse level (step 2). Thus, a non-magical commoner with a 12 charisma could normally cast a maximum of a level 1 curse, but if he applies modifiers wisely, he may manage to change a base level 4 curse into a curse of level 1 after final calculations are made.
Note that the charisma modifier level cap only applies to those who are not using spell slots. A wizard with a charisma of 12 can cast a level 9 curse if he or she has a level 9 spell slot available. Spell slots bypass the charisma limitation. However, if that same wizard did not prepare a curse in a spell slot and wants to cast a curse on-the-fly in his death throes, then he suddenly is limited to what his charisma will allow (because effectively, the wizard is casting outside his normal spellcasting ability, and is suddenly drawing upon his own force of personality to power the spell, just as a non-magical commoner would).
Step 2
Determine the starting or base curse level. This uses pages 61-64 of The Practical Enchanter. You select your type of curse and follow its level restrictions (types listed include ability score penalties, confusion, die roll penalties, antipathy, afflictions, compulsions, dooms, enmity, prohibitions, and transformations).
Note that any curse that reproduces (or closely resembles) an existing spell must be at least 1 level higher than the existing spell. In some cases, the text in The Practical Enchanter may require the curse to be many levels higher. Curses are intended to be weaker than normal spells, and if a curse is set to reproduce a spell effect regularly then it certainly cannot be the same level as a normal, one-time-use spell.
Step 3
Apply modifiers. This uses page 60 of The Practical Enchanter. Mandatory modifiers are range, target, and duration. In addition, casting time as listed on page 60 is overruled. A curse is a full action by default. Shortening the casting time to a standard action increases the level modifier by 1. Shortening to a swift or immediate action (your pick) increases the level modifier by 1 again (so a total of +2 to the level of the curse, if you wish to cast it as an immediate action). Immediate action curses are what allow, for example, a farm hand to issue a curse with his dying breath.
In addition, there is a table showing extra modifiers that may (or may not) apply. One of those modifiers is an optional XP cost. That modifier is replaced with a flat level cost (similar to a level drain, but a full reversion to a lower level). These stack, so if you have 3 levels you are willing to sacrifice, you can reduce the spell level by 3. For purposes of determining your remaining XP, the system follows the DMG, page 296 ("your level loss sets your XP at exactly the midpoint between your old & new XP score"). Note that while spellcasters might have to do this to get a spell to fit into an available spell slot, people who are not using spell slots should avoid it, as it lowers the DC unnecessarily. Step 4 offers a "buy up" system that costs the same (levels) but keeps the DC high.
Step 4
"Pay" for your spell. If you are a spellcaster with available openings, then the cost is simply the use of a level-appropriate opening. If a curse is of a level lower than 0, it still takes up a level 0 slot. You may proceed to step 5.
If you are unable to use a spell slot for any reason, you must "buy up" to the level of the curse, using your own life force. Start at -5, and buy your way up, using 1 level worth of XP from your character for each level up you need. In other words, if you created a level 0 curse, you would need to sacrifice 5 of your own character levels to go from the starting point of -5 up to level 0. If you don't have the levels, you don't have enough life force to cast the curse. You may modify the level of the curse, if possible.
Note that this technically means that a curse of level -5 (or lower) is free -- someone with no spellcasting ability could cast these curses over & over again. However, a curse of level -5 is typically extremely weak, and requires heavy modifiers to get it down to such a level. Generally, the non-spellcaster will be losing his or her life in the process (since "mortal blow" grants such a nice level modifier).
Step 5
Change the alignment descriptor, if necessary & possible. Generally, the descriptor for a curse is "Evil." However, a curse placed via opposing alignments may change that. For example, a good person casting a curse on an evil person would change the descriptor to Good. A lawful person casting a curse on a chaotic person would gain the Lawful descriptor, and vice versa. This is contingent upon the alignment of the caster and the victim being opposed. A good person casting a curse upon a good or neutral person would not grant the curse a Good descriptor. A paladin cannot, for example, curse his own lawful good organization and expect his curse to gain the Good descriptor. In such a case, the curse remains Evil. However, a paladin defending a town from the onslaught of genuinely evil drow could make a dying curse against them -- his lawful good opposing their neutral evil would net the curse a descriptor of Good. Similarly, that same paladin cursing the chaotic evil demon Hezrou would cause the curse to have two descriptors -- Lawful and Good.
Removing Curses
Note the following changes to the rules for removing curses (page 65). Break Enchantment will remove any curse with a base level (as determined in step 2) of 5 or lower. Remove Curse will remove any curse at all, however the spellcaster must be double the curse's base level. So to remove a 3rd-level curse, the caster must be level 6. To remove a 9th level curse, the caster must be level 18. Greater Remove Curse doesn't exist, so you can ignore mention of it in the book's text.
Example
Let's take an almost-worst-case scenario -- let's say you're playing a level 0 commoner (a person with no levels of any class) with a charisma of 4. This person can only cast curses of level -3 (or lower), due to the charisma modifier capping his/her casting level. In addition, without having any levels of any class, this person cannot "buy up" to the -3 spell level by sacrificing his/her own character levels. Therefore, he or she will need to start with a low-level curse and then apply other modifiers extensively until the spell is level -5 (which has been previously noted as the free "ground zero" for casting a curse). So perhaps start with a curse that causes a pet to turn on its owner -- this is a level 1 enmity curse (page 63). Then give the curse a lengthy delay in taking effect (-1) so that the level is now 0. And because the pet owner killed your kids (-1) and will kill you momentarily (-2), that lowers the curse by 3 so that it is now level -3. Finally, because the pet owner who is about to kill you is also a relative (-1) and is so incredibly powerful that you cannot fight back effectively (-1), the spell falls two more levels, down to -5. Thus, a level 0 commoner with almost no force of personality may be able to cause some minor harm to his/her killer, even though he or she is not a spell caster.
The DC
The DC is a Will save, calculated normally if you're using spell slots. Otherwise, the DC is 10 + the spell's calculated level (step 3) + the charisma modifier. In the example above, the spell is level -5, and the person's charisma modifier is -3 -- that's -8 plus 10 = 2. So the cursed person needs to make a Will save of 2 or better to save against it. Obviously, these curses are pretty weak and often ineffectual when cast by the lowest of the low -- but it's still some kind of magic for those who have no magical abilities at all and no other hope. And for those with even a few levels of Commoner (or Expert, or any other class) and a decent charisma, the curses can make the downtrodden downright dangerous.
Conclusion
The general idea here is to help to enable traditional folklore situations (where someone suffers great transgressions before issuing a curse) without causing curses to become a common parting gift for every non-magical person in your game world. This system seems to work that way -- extreme hardship may enable it, but it isn't common.
In addition, because curses are essentially custom spells that the player & DM must agree upon, I did not want to make them equal to or better than normal spells, as then power gamers would constantly use curses, slowing down gameplay for everyone as they tried to create optimized spells on the fly, every time. However, for players who are really stuck and have no other options, sitting down with this system for 10 minutes might be a real viable way to "go out with a bang" at the end of a TPK. It might also help to enable scenarios where the players have to find non-combat ways to overthrow an incredibly powerful ruler or something similar.
I hope it helps.
Much thanks to Paul M. Melroy for writing the original system in The Practical Enchanter, and to Patrick Bryant for releasing it for free.
I am going to present here a modified version of that curse system which does allow curses to be used by anyone, including PCs & commoners. However, curses default to the Evil descriptor, so paladins generally wouldn't use a curse. Circumstances can change the descriptor, so nothing is written in stone.
If you are able to cast spells, you can use curses as if they were normal spells. Generally, you wouldn't do this, as normal spells are more powerful. However, if you are up against an enemy that is too powerful, this curse system would allow you to issue curses from a safe distance. In addition, with careful application of modifiers, you can cast a curse that is far more difficult for the enemy to remove than a normal "Bestow Curse" spell.
If you are not able to cast spells, you can sacrifice levels in order to cast a curse. If you are a spellcaster but did not chose a curse as one of your daily spells, you may also opt to sacrifice levels to cast a curse. While that may seem like an incredibly unappealing way to create a spell effect, since curses are typically used by people who are desperate or dying, they often don't care about the level loss anymore.
Limitations
You cannot cast a dying curse (using an immediate action to get your curse out before the killing blow lands) if you are flat-footed or otherwise unaware of the impending strike.
Curses are powered by malevolent spirits. If you use a curse in a normal spell slot, you essentially bind a spirit to your cause. In so doing, you need not worry or track what happens next. The spirit will do its work, and you are free to go on your way.
However, if you cannot use spell slots, you end up using your own spiritual force to power the curse. This means you cannot come back to haunt someone as a ghost (or anything else). This means you cannot be brought back to life. Your soul has a prior engagement, so to speak. Of course, if the curse is lifted, then hauntings and new life may be possible (but if you have cast multiple curses this way, all of them must be lifted, first).
Based upon the prior paragraph, you may deduce that it is also impossible for the undead to cast curses, unless they have spell slots. This is because an undead without spell slots would need to commit its soul to the curse, but the soul is already being used to power their undead form! Or in some cases, their undead form is not tied to any soul at all (such as skeletons & zombies), and thus there is no soul available to power such a curse. This limitation should be extended to any creature that does not have a soul, such as a construct.
As an aside, because curses are actually powered by something that has some kind of sentience, you should expect that curses will not be convenient for the cursed. For example, someone cursed to hear voices (affliction curse, page 62) will not get to declare "the voices only happen at night and I sleep through them." Instead, the curse will likely cause the voices to occur at a time when the cursed person really wouldn't appreciate it. Note that whatever these sentient, malevolent spirits are, they are not prescient, so they cannot always time their effects for the most perfectly disruptive moment. They simply execute the curse to the best of their limited abilities.
Step 1
Determine the level cap of the curse you wish to cast. As a spellcaster, a curse can fill any slot you have open, but no more. Curses work just like spells for you, with DCs calculated as is normal for your class. You can move on to step 2.
If you do not have slots open (or are not a spellcaster), you default to your charisma modifier as your maximum spell level. Since curses can be negative levels, it's still possible for someone with a terrible charisma score to cast a curse (for example, a character with a charisma of 6 could cast up to a level -2 curse). Note that this limitation applies to the calculated curse level (step 3), not the base curse level (step 2). Thus, a non-magical commoner with a 12 charisma could normally cast a maximum of a level 1 curse, but if he applies modifiers wisely, he may manage to change a base level 4 curse into a curse of level 1 after final calculations are made.
Note that the charisma modifier level cap only applies to those who are not using spell slots. A wizard with a charisma of 12 can cast a level 9 curse if he or she has a level 9 spell slot available. Spell slots bypass the charisma limitation. However, if that same wizard did not prepare a curse in a spell slot and wants to cast a curse on-the-fly in his death throes, then he suddenly is limited to what his charisma will allow (because effectively, the wizard is casting outside his normal spellcasting ability, and is suddenly drawing upon his own force of personality to power the spell, just as a non-magical commoner would).
Step 2
Determine the starting or base curse level. This uses pages 61-64 of The Practical Enchanter. You select your type of curse and follow its level restrictions (types listed include ability score penalties, confusion, die roll penalties, antipathy, afflictions, compulsions, dooms, enmity, prohibitions, and transformations).
Note that any curse that reproduces (or closely resembles) an existing spell must be at least 1 level higher than the existing spell. In some cases, the text in The Practical Enchanter may require the curse to be many levels higher. Curses are intended to be weaker than normal spells, and if a curse is set to reproduce a spell effect regularly then it certainly cannot be the same level as a normal, one-time-use spell.
Step 3
Apply modifiers. This uses page 60 of The Practical Enchanter. Mandatory modifiers are range, target, and duration. In addition, casting time as listed on page 60 is overruled. A curse is a full action by default. Shortening the casting time to a standard action increases the level modifier by 1. Shortening to a swift or immediate action (your pick) increases the level modifier by 1 again (so a total of +2 to the level of the curse, if you wish to cast it as an immediate action). Immediate action curses are what allow, for example, a farm hand to issue a curse with his dying breath.
In addition, there is a table showing extra modifiers that may (or may not) apply. One of those modifiers is an optional XP cost. That modifier is replaced with a flat level cost (similar to a level drain, but a full reversion to a lower level). These stack, so if you have 3 levels you are willing to sacrifice, you can reduce the spell level by 3. For purposes of determining your remaining XP, the system follows the DMG, page 296 ("your level loss sets your XP at exactly the midpoint between your old & new XP score"). Note that while spellcasters might have to do this to get a spell to fit into an available spell slot, people who are not using spell slots should avoid it, as it lowers the DC unnecessarily. Step 4 offers a "buy up" system that costs the same (levels) but keeps the DC high.
Step 4
"Pay" for your spell. If you are a spellcaster with available openings, then the cost is simply the use of a level-appropriate opening. If a curse is of a level lower than 0, it still takes up a level 0 slot. You may proceed to step 5.
If you are unable to use a spell slot for any reason, you must "buy up" to the level of the curse, using your own life force. Start at -5, and buy your way up, using 1 level worth of XP from your character for each level up you need. In other words, if you created a level 0 curse, you would need to sacrifice 5 of your own character levels to go from the starting point of -5 up to level 0. If you don't have the levels, you don't have enough life force to cast the curse. You may modify the level of the curse, if possible.
Note that this technically means that a curse of level -5 (or lower) is free -- someone with no spellcasting ability could cast these curses over & over again. However, a curse of level -5 is typically extremely weak, and requires heavy modifiers to get it down to such a level. Generally, the non-spellcaster will be losing his or her life in the process (since "mortal blow" grants such a nice level modifier).
Step 5
Change the alignment descriptor, if necessary & possible. Generally, the descriptor for a curse is "Evil." However, a curse placed via opposing alignments may change that. For example, a good person casting a curse on an evil person would change the descriptor to Good. A lawful person casting a curse on a chaotic person would gain the Lawful descriptor, and vice versa. This is contingent upon the alignment of the caster and the victim being opposed. A good person casting a curse upon a good or neutral person would not grant the curse a Good descriptor. A paladin cannot, for example, curse his own lawful good organization and expect his curse to gain the Good descriptor. In such a case, the curse remains Evil. However, a paladin defending a town from the onslaught of genuinely evil drow could make a dying curse against them -- his lawful good opposing their neutral evil would net the curse a descriptor of Good. Similarly, that same paladin cursing the chaotic evil demon Hezrou would cause the curse to have two descriptors -- Lawful and Good.
Removing Curses
Note the following changes to the rules for removing curses (page 65). Break Enchantment will remove any curse with a base level (as determined in step 2) of 5 or lower. Remove Curse will remove any curse at all, however the spellcaster must be double the curse's base level. So to remove a 3rd-level curse, the caster must be level 6. To remove a 9th level curse, the caster must be level 18. Greater Remove Curse doesn't exist, so you can ignore mention of it in the book's text.
Example
Let's take an almost-worst-case scenario -- let's say you're playing a level 0 commoner (a person with no levels of any class) with a charisma of 4. This person can only cast curses of level -3 (or lower), due to the charisma modifier capping his/her casting level. In addition, without having any levels of any class, this person cannot "buy up" to the -3 spell level by sacrificing his/her own character levels. Therefore, he or she will need to start with a low-level curse and then apply other modifiers extensively until the spell is level -5 (which has been previously noted as the free "ground zero" for casting a curse). So perhaps start with a curse that causes a pet to turn on its owner -- this is a level 1 enmity curse (page 63). Then give the curse a lengthy delay in taking effect (-1) so that the level is now 0. And because the pet owner killed your kids (-1) and will kill you momentarily (-2), that lowers the curse by 3 so that it is now level -3. Finally, because the pet owner who is about to kill you is also a relative (-1) and is so incredibly powerful that you cannot fight back effectively (-1), the spell falls two more levels, down to -5. Thus, a level 0 commoner with almost no force of personality may be able to cause some minor harm to his/her killer, even though he or she is not a spell caster.
The DC
The DC is a Will save, calculated normally if you're using spell slots. Otherwise, the DC is 10 + the spell's calculated level (step 3) + the charisma modifier. In the example above, the spell is level -5, and the person's charisma modifier is -3 -- that's -8 plus 10 = 2. So the cursed person needs to make a Will save of 2 or better to save against it. Obviously, these curses are pretty weak and often ineffectual when cast by the lowest of the low -- but it's still some kind of magic for those who have no magical abilities at all and no other hope. And for those with even a few levels of Commoner (or Expert, or any other class) and a decent charisma, the curses can make the downtrodden downright dangerous.
Conclusion
The general idea here is to help to enable traditional folklore situations (where someone suffers great transgressions before issuing a curse) without causing curses to become a common parting gift for every non-magical person in your game world. This system seems to work that way -- extreme hardship may enable it, but it isn't common.
In addition, because curses are essentially custom spells that the player & DM must agree upon, I did not want to make them equal to or better than normal spells, as then power gamers would constantly use curses, slowing down gameplay for everyone as they tried to create optimized spells on the fly, every time. However, for players who are really stuck and have no other options, sitting down with this system for 10 minutes might be a real viable way to "go out with a bang" at the end of a TPK. It might also help to enable scenarios where the players have to find non-combat ways to overthrow an incredibly powerful ruler or something similar.
I hope it helps.
Much thanks to Paul M. Melroy for writing the original system in The Practical Enchanter, and to Patrick Bryant for releasing it for free.