In Search of Flexible Defense Mechanics

[Sacrosanct]

One of the things I'm really trying to nail down is a way to make defense something other than a static value. To add flexibility and options for the players. I've had several ideas, and after playtesting sessions there's always something significant to change. It just doesn't quite feel right yet, so I'm reaching out beyond for ideas and suggestions.

What I mean by flexible defense
Most rpgs that I know of handle defending against an attack like this: Attacker needs to beat a target defensive value in order to hit. 90% of the time that number doesn't change. Sure, sometimes it's different based on factors (3e famously has a few ACs depending on what was going on), but it was still largely the same number whether you were being attacked by one person in a round or ten. Sometimes you could boost that target # via several means (spells, dodging, etc.), but again, the number stayed pretty static regardless of who or what was actually attacking you.
What I'm looking for is a way for the PC to adapt to what's happening in the round and react accordingly. Something to capture the idea that it's harder to defend against multiple attackers than it is against one. Something kinda sorta like spell points for Armor Class (not really, but for illustrative purposes). If you have a pool of defensive ability in a round, maybe you don't worry so much about the mooks attacking you, but focus your defense on a tougher opponent.

Why I want to do this
It's just one way of many to allow martial and mundane PCs have more stuff to do in combat. One round they may act like a tank, while the next go on offense. It models the verisimilitude I prefer in how a combat encounter looks like against multiple opponents--shields can't block every attack at the same effectiveness and being swarmed matters (this part is subjective, I know). I think it adds a new facet to the combat encounter that's largely overlooked.

Assumptions
The best way I'm handling the overall mechanics is to use a dice pool system. From here on out, assume we're using this system so try to keep suggestions based on this system. Much like RISK, both sides roll their dice pools and whoever has the highest value wins. If an attacker rolls a 5 and you roll a 4 as your highest, the attack hits. I prefer this method because there's no math in the actual combat resolution phase. No modifiers to add or subtract. The die type and amount may change, but you're always just looking at the highest result.
Damage is a similar mechanic. You roll your damage pool and take the highest result. More dice in your pool = better chance of more damage, especially if you trade up (see below). Getting more than one success can do different things. You can either increase damage or enforce some other effect (like pushing, distracting, etc.).

Current iteration I'm on
Right now, a defenders DEF dice pool is based on what level tier they are to determine die type (called a Proficiency Die, or PD), and the amount of dice is based on shields, traits, and maneuvers. For example, a low level PC (1st tier) would have a d6 as their PD, and have a pool of 2d6 based on a light shield (1d6) and a trait they've chosen (+1 die). A low mid tier PC might have a d8 for the PD, and have a pool of 4d8 based on a heavy shield (3d8) and the trait they've chosen (+1 die). And so on. You get the idea.
Whenever you are attacked in a combat round, you roll at least one PD for your DEF. You then decide how many of the dice in your pool you will allocate to defending that attack. As previously stated, if the attacker’s highest die beats the highest die that you allocated, the attack succeeds.
Against any further attacks, you allocate any remaining DEF dice as you wish. When you no longer have any DEF dice left in your pool, you roll only 1 PD for DEF from that point on.

The flexible part

• This allows the player to decide if they want to focus on defending against a specific attacker or not.
• You can also trade in two dice of one type for the next highest type, or one higher type for two lower types. E.g., trade in 2d6 for 1d8 or 1d8 to 2d6. You're weighing the risk of getting a higher result at the cost of a more swingy result.
• You can also trade in DEF die to gain a bonus on other things (like attacking, or a special maneuver).

Can you show me?
The following illustration explains it a bit better using visual references. At least I hope

My conundrum
I don't think I'm still sold on it. I feel like there's a gap somewhere that I'm missing, or a cool way to utilize the pools I'm missing. Fresh eyes would be great.

 

[DrunkonDuty]

Hero System has skill levels. This is basically a pool of bonuses that can be shifted around as you want.

You can buy a skill level for pretty much anything. Combat skill levels can be applied to attack, defence, or damage as the player desires. You could buy them for all combat, or just for melee combat, or just for sword combat. Whatever you want really.

So let's say your character has +4 skill levels with melee combat. At the start of of their turn they can rearrange what those skill levels can be applied to. They can be split between melee attack, melee defence, & melee damage as desired. Say, 1 for attack, 1 for defence, 2 for damage. Next time they act they decide they need to go all defensive, so they put all 4 into defence. Skill levels must be assigned at the start of a character's turn, they cannot be changed until the start of the characters' next turn. If a player forgets to assign skill levels they are assumed to stay where they were last put.

I'm not sure how easily this will translate to your system. Since it's a dice pool, maybe being able to rearrange what dice are where when you act sounds like the obvious answer, but I'm not sure.

 

[Sacrosanct]

Hero System has skill levels. This is basically a pool of bonuses that can be shifted around as you want.

You can buy a skill level for pretty much anything. Combat skill levels can be applied to attack, defence, or damage as the player desires. You could buy them for all combat, or just for melee combat, or just for sword combat. Whatever you want really.

So let's say your character has +4 skill levels with melee combat. At the start of of their turn they can rearrange what those skill levels can be applied to. They can be split between melee attack, melee defence, & melee damage as desired. Say, 1 for attack, 1 for defence, 2 for damage. Next time they act they decide they need to go all defensive, so they put all 4 into defence. Skill levels must be assigned at the start of a character's turn, they cannot be changed until the start of the characters' next turn. If a player forgets to assign skill levels they are assumed to stay where they were last put.

I'm not sure how easily this will translate to your system. Since it's a dice pool, maybe being able to rearrange what dice are where when you act sounds like the obvious answer, but I'm not sure.

That’s kind of what I’m thinking as well.

 

[DrunkonDuty]

I'm a big fan of it. It gives characters flexibility that nicely mimics cinematic action and, most importantly, increases the player's agency.

 

[RangerWickett]

What I'm looking for is a way for the PC to adapt to what's happening in the round and react accordingly. Something to capture the idea that it's harder to defend against multiple attackers than it is against one.

I have pursued this for a long time. I've tried lots of things, but nothing that's really easy to just slot into existing D&D without a lot of changes.

It looks like you're trying to build a whole new combat system, though. Or are you intending to layer this over D&D as is?

I worry about the, like, ineffectiveness of many turns. If I roll dice and you roll dice, that's a lot of physical activity and number tracking, but about half of turns nothing happens, right? I mean, in a real fight, sure, there's a lot of probing that accomplishes nothing, but combat already takes a lot of time at the table. Personally I'd rather have a system where stuff happens each turn.

I think there's a way to get the feel you want with less time spent just chucking dice that don't actually progress the combat narrative.

Something kinda sorta like spell points for Armor Class (not really, but for illustrative purposes).

Well that is basically just Hit Points.

Fresh eyes would be great.

I've made a lot of attempts at building systems with flexible offense/defense systems. Let me mention a few in quick procession of increasing deviation from D&D norm:

Stances
Each turn you pick one of five stances at the start of your turn. The stances give you one reaction you can take. The default stance is Alert, which lets you make opportunity attacks. If you choose a different stance, you can't make OAs.

Brandish stance lets you use a reaction to attack someone who moves within reach of your weapon (or who exposes themselves within 30 ft if you have a ranged weapon), but after you use the reaction, enemies have advantage on attacks against you until the start of the next turn. High risk, but potentially high reward.

Close stance gives you no reaction. Instead you choose a foe within reach who has no weapons (or natural weapons), or a foe that either you're grabbing or who has grabbed you. You and that enemy are restrained as long as you're adjacent (speed 0, disadvantage on Dex saves and attacks, and attackers have advantage against you).

Defender stance lets you use a reaction to impose disadvantage on a single attack if the attacker or target is within your reach. (It's a bit more fiddly than that, because ranged attacks are weird, but that's the gist.)

Evasive stance lets you use a reaction to move half your speed when targeted by something, but then you're slowed on your next turn. After the movement happens, your opponent can use more of their movement to try to still hit you. It's most useful for leaping to cover to avoid ranged attacks or to get out of the area of fireballs.

Also I thought of maybe having a Focus stance, that grants no reaction but gives you some perk (like it charges up limited-use abilities) or lets you recover HP if you can go a whole round without getting hit.

Aegises
Inspired by the way the Fantasy Flight Games edition of the Legend of the Five Rings card game did its victory condition. In L5R you don't just have a life total like in Magic: the Gathering. You have four provinces and one stronghold, and with each attack your opponent targets one of the provinces (each of which has some effect - maybe a perk that helps you, or a backlash that punishes the attacker).

Only once they've broken three provinces can they attack the stronghold, and they have to break the stronghold to win the game.

In a TTRPG form, this would require a lot of special design. Like, maybe each turn you pick one aegis to be active, and if your enemies do at least X damage to you, they break your aegis and you've got to switch to a new defensive style. Like maybe one aegis is "swashbuckling" and it lets you move faster when you have it active, and attacks with light weapons do less damage because you can parry them, while a fire wizard might have "fire shell" which does a bit of fire damage to people who attack, but cold damage against them is increased?

It would require a lot of design to make interesting options that don't feel too "disassociated" from the narrative, though.

Streets of Rage(sia)
The War of the Burning Sky adventure path involves an empire called Ragesia. One of my friends made a joke about the beat-em-up video game Streets of Rage turning into Streets of Ragesia, and I, well, designed a whole combat system around it.

The gist is that each player has a pool of 6d6, and they have a roster of abilities that cost dice of a certain value. At the start of the turn, each player rolls all their dice and keeps the results. Then people take turns spending dice to do stuff.

A light attack might cost a die of value 2 or higher. A special move might cost 4 or higher. A super move costs 6. You can use dice of value 1 to do stuff like dash, grab, and trigger non-damaging abilities.

The thing is, you don't roll to attack. If you spend a die, you succeed at the thing (some exceptions apply with bosses). But it's engaging because you play your turn differently each time because you have slightly different options, and each character has some abilities that combo well with other players - but those players have different dice each turn, so you aren't always spamming the same combos.

As for enemies, mooks only roll 1 die, and they roll it whenever they take their turn. Each mook would have 2 abilities - one attack (that might cost 2+ or 4+) and one gimmick (that can be triggered with a 1+ die). If a mook rolls a 6, they roll an extra die and get to take two actions.

So if you've got like 4 PCs versus 12 mooks, the turn would start, and the four PCs would each roll 6d6 and set them aside. Then play would progress back and forth, with one PC, then one mook, then another PC, then another mook. Each time, someone spends a die (or a mook rolls a die to see what he does), and the mooks would typically end up finishing first because they have a total of 12 actions (well, 14 on average with exploding dice), while the PCs get 24 actions.

To add a smidge of complexity, each PC also gets a once per combat "defensive save" that blocks an incoming attack and does something nifty.

---

I really like my Streets of Ragesia design, but sadly I haven't managed to get my players to test it yet.

 

[pemerton]

In Rolemaster, at the start of each round, any PC in melee must assign some portion of their weapon skill bonus to attack (Offensive Bonus, or OB) and some of that same bonus to parrying (Defensive Bonus, or DB). Generally parry DB only applies against one opponent.

In Burning Wheel's Fight! sub-system, each character/creature has a number of action determined by their Reflex attribute (generally 3 to 5, though fewer or more are both possibilities for some outliers). At the top of each "exchange", each combatant has to script 3 "vollyes". Each volley has actions allocated to it, so that (i) the total number of actions in an exchange equals Reflex, and (ii) the actions are spread as evenly as possible over the volleys (so eg Reflex 3 means 1 action per volley; Reflex 5 means two volleys will have two actions, and one will have one).

Once scripting is done, volleys are revealed one at a time, with action resolved simultaneously and in sequence.

The basic attack action is Strike. How it resolves depends on what (if anything) is scripted against it. Eg if Block is scripted, then opposed rolls are made. If Avoid is scripted then, opposed rolls are also made but the defender (to use D&D jargon) rolls on DEX rather than weapon skill. If Counter-strike is scripted, then the weapon pool must be split, with some used on defence similar to a Block, and some used on attack similar to a Strike. There are other options, such as Feint which automatically fizzles against a Strike but automatically cuts through a Counter-strike. Different weapons also have attributes that include how frequently, in an exchange, they can be used to Strike (this is the system's equivalent of weapon speed).

If a Strike succeeds, armour gives a separate pool of dice to roll to negate the (threatened) injury. Some weapons step up the difficulty of this armour test.

Obviously it's a fairly intricate system, and it doesn't need to be used for every physical altercation. But when it is used, it does generate variation and surprise, and a skilled player can do better than their raw stats would suggest by dint of clever scripting.

 

[dbm]

GURPS use an active defence system which differentiates between dodge, parry and block and puts constraints on all of the above.

As a side note, by default martial characters have far more tactical options than wizards in GURPS.

You can see the bones of the system in the free Lite rules [link].

 

[Nutation]

Steve Perrin in some of the games he designed or ran (RIP) had the defender roll vs. the attacker's static value instead of the normal way. His theory was that the attacker is already doing things (move, choose an attack), and this lets one more player do things on any given character turn.

 

[schneeland]

Because of early exposure, namely Shadowrun, active defense feels much more normal to me (static defense values are something I associate primarily with D&D and offspring). Now Shadowrun is maybe not something I would recommend to adapt 1:1, but maybe there's something here and there that's still helpful. If I remember correctly, in melee both attacker and defender roll for combat - each with individual modifiers affecting the target number - and whoever rolls more successes wins and gets to roll damage and the loser gets to roll soak (based on armor and other defensive modifiers). The details were much more involved, but I don't remember them accurately (the last edition I played for a longer time was 2e in the 90s).
If you want a lighter system, you could look to Forbidden Lands, were also both attacker and defender roll. Similar to what @dbm describes for GURPS, the defender can choose to dodge or parry. Attackers, on the other hand, assuming they have the right weapon, can choose to use their fast action (for the most part, characters have a fast and a slow action) to build up momentum and hit harder (I think +1 die for the dice pool of the attack) - among others, this means you can "buy" additional damage for excess successes. However this will cost the character the opportunity to do an active defense in the same round, increasing the risk for severe injury.
And if you want to go very light-weight, you could have a look at Warlock! (a Fighting Fantasy-descendant) where both parties roll their respective combat skill, and the higher one wins (in melee, attackers get a +5 bonus). If the winner beats the loser by a factor of 3, it's a critical hit.

 

[Sacrosanct]

And if you want to go very light-weight, you could have a look at Warlock! (a Fighting Fantasy-descendant) where both parties roll their respective combat skill, and the higher one wins (in melee, attackers get a +5 bonus). If the winner beats the loser by a factor of 3, it's a critical hit.

That's kinda how this works. Except for critical hits as the baseline, additional success can be used for the following (CD = Core die, think of it like a hit die in D&D, and vigor is a pool that powers maneuvers and abilities):

Spend 1 additional success to:
add a CD to the attack/ability/spell’s effect (if it uses a CD as part of the original description).
reduce the AP cost of your next action against the same target by 1 until the start of your next turn.
reduce the vigor cost of your next action against the same target by 1 until the start of your next turn.
increase the duration of the ability/power/spell by 50% (rounded up).
increase the range of the ability/power/spell by 50% (rounded up).
increase the jump distance, climbing/swim speed, etc. by 25% (rounded up).

Spend 2 additional successes to:
add +2 CD to the attack/ability/spell’s effect (if it uses a CD as part of the original description).
reduce the vigor cost of your next action against the same target by 3 until the start of your next turn.
double the duration of the ability/power/spell.
double the range of the ability/power/spell.
increase the jump distance, climbing/swim speed, etc. by 50% (rounded up).
gain resistance to the damage type prompting your CR until the end of your next turn.
impart vulnerability to the target of the damage type of your attack until the start of your next turn.

Spend 3 or more additional successes to:
add +3 CD to the attack/ability/spell’s effect (if it uses a CD as part of the original description).
add 1 CD to your BDP of the attack or spell.
reduce the vigor cost of your next action against the same target by 5 until the start of your next turn.
reduce the AP cost of your next action against the same target by 2 until the start of your next turn.
recover the vigor cost of the action you just took.
triple the duration of the ability/power/spell.
triple the range of the ability/power/spell.
double the jump distance, climbing/swim speed, etc.