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Oh, Injury!

We use this rule set in conjuction with Introducing late night fighting; they work on a separate layer and you can use one without using the other, and vice versa.

So many people across multiple forums have helped me work on this, and my own group has helped me so much. The initial idea came from Paul Taliesin. You can also find other precedents here.

This a September 2020 complete rewrite of the June 2019 original. It’s around 30% shorter and hopefully much clearer.

The Pitch

HP is no longer “meat points”; it’s points that you spend in order to avoid getting hurt.

— “The skeleton is about to chop off your arm with her shortsword!”
— “Clang! I block with my own sword!”
— “OK, it costs 1d6+2 HP to do that.”

You are getting exhausted as you are trying to stave off death.

You can describe all kinds of defensive stunts, rolls etc, as long as you are able to pay. They don’t cost actions, reactions or bonus actions, they just cost HP.

The Two Lines of Defense

The HP pool is the second line of defense after armor class.

You can use this idea together with the normal “monsters roll versus AC” rules. In that case, rolls under AC might sound like “OK, the skeletons are still casing you out, Alice, they’re trying to find an opening” and similar. Only when the monsters roll your AC or higher will the DM describe them as serious threats as described above.

Defense Rolls

The other way is to use “defense rolls”. Instead of writing your AC on your sheet, write your “defense mod” (which is what the normal AC would be minus twelve, so AC 10 = -2, AC 14 = +2 etc). You only need to do this as you create or equip your character.

And then the DC for making defense rolls is very easy for the DM to figure out. A +3 attack is 13, a +7 attack is 17, a +1 attack is 11 etc. (You add ten, which often just means reading the plus sign as if it were a one.)

With this method, the DM describes all attacks as if they were serious, but players have two lines of defense. The defense roll, and then if that fails, spending HP.

— “The skeleton swirls around, trying to come at you with her shortsword, like this.”
— “I bring up my shield!”
— “OK, make a defense roll vs 14.”
— “I failed!”
— “The shield is too slow, and the skeleton is about to chop off your arm with her shortsword!”
— “Clang! I block with my own sword!”
— “OK, it costs 1d6+2 HP to do that.”

If you roll a natural one on your defense roll, the monster’s attack is a critical hit.

Neither defense rolls nor HP spending costs action and you can describe either freely. Maybe your Mage Armor means birds fly out to eat the bullets? Just as long as your two lines of defense are different from each other. One can be a shield block, and the other a parry (and next round maybe vice versa). Other ideas include dodging, ducking, stepping over, using your armor…

At 0 HP

When you run out of HP and you can’t pay is when a hit finally lands. The normal rules apply with unconsciousness, death saves, death save failures and so on.

Just as in the RAW, when monsters attack the fallen bodies they inflict death save failures instead of HP loss. Death save failures is the true “meat points” of 5e. Each hit is a death save failure, but crits are two death save failures, and any hit within 5 feet on an unconscious creature counts as a crit (and they get advantage too—check the Conditions chapter).

I like to apply a lingering injury as they reach 0 HP (an optional rule from the DMG, p272).

Injury Rolls

1–3
Lose what’s most appropriate from arm, hand, foot, leg or eye. (If unknown: 1: eye, 2: arm, 3: leg.)
4–6
Horrible scar
7–10
Minor scar
11–14
Broken bone or swollen eye. Function is temporarily lost as above, but any magical healing restores it. A swollen eye heals up by itself in 24h. (If unknown: 11: limp, 12–14: broken ribs.)
15–17
Internal injury
18–20
Festering wound

For explanations of the entries, see DMG p272.

This is a reorganization of the table from there; it has the same things on there with the same probabilities, but with two changes.

First of all, things are moved around so that anything that’s goes away with low-level magical healing is on an 11+. Cure wounds can cure those wounds.

Second, the original table also work as a kind of hit location table. I’ve preserved that with the If unknown parentheses but since you are describing your blows so carefully when using Oh, Injury, you often know exactly what body part is in danger and it feels weird to roll “you lose a leg” when the guy was chopping at your arm.

Other Moves

Since you’re describing everything, feel free to, as appropriate, use rules for grappling, shoving, disarming, climbing on the enemy etc (some of those are from the DMG’s section of optional rules).

Here’s an example.

— “I swing my sword as hard as I ever-lovin’ can, tryna knock it’s sword out of its hand”
— “Roll an attack roll, vs 12 instead of the normal 13.”

Because my thinking as DM in that situation might be that it triggers an attempt to Disarm (DMG p271), and the monster will defend with strength (+2, and I use a flat 10 for monster’s opposed rolls) instead of AC.

This is one of the goals of this system; to get the game grounded in free description of what you do rather than selecting from a set list of canned moves.

If They Don’t Defend

Wounds

Wounds are inspired by the “Festering Wound” injury entry, detailed on the DMG p 272.

When you have a wound, you lose 1 max HP every morning. Any magical healing, or the “Healer” feat, gets rid of all wounds instantly.

The other way to get rid of them is more cumbersome. It takes ten successful DC 15 wisdom (medicine) checks, from yourself or someone else but each patient can only recieve one such check per day. Each single use of a Healer’s kit (PHB p151) counts as one automatic successful check out of these ten. (So over ten days you could spend one entire Healer’s kit to cure someone’s wound.)

Failing does not reset the success count; the ten successes don’t have to be consecutive. But, after the first failure the wound now counts as “festering”, which changes how it’s described but the only mechanical difference is that the “Healer” feat doesn’t work anymore, the cure has to be magical or the ten-checks-method.

If player characters don’t defend themselves, hand out a wound and note the HP cost just as you would with a ‘messy’ attack, below.

In extreme cases, like let’s say it’s their own gnome mom attacking them and they don’t want to defend, hand out death save checks, death save failures, even unconsciousness.

‘Messy’ Attacks

Some monster attack abilities are ‘messy’; they grapple you, paralyze you and other horrible things. (Thanks to Dungeon World for this term.)

What Is Not Messy?

Most attacks aren’t ‘messy’, and monster attacks that just conditionally cost more HP are not ‘messy’ in this sense either. For example, a poisoned blade but all the poison does is dealing extra damage on a failed con save.

Just have them roll the save and if they fail, pay the HP to yank that arm away or parry it — as long as they can afford it, it never grazed skin.

An example:

— “The skeleton is about to chop off your arm with her poisoned shortsword!”
— “Clang! I block with my own sword!”
— “OK, it costs 1d6+2 HP to do that, and 3d6 more unless you can make a DC 12 con save.”

The diegetic explanation is that you exert more effort to avoid getting scratched by poisoned weapons when your constitution is low enough to be susceptible to the poison. Even if you don’t know that the blade is poisoned; your HP is a mix of fatigue and, uh, let’s call it “destiny”.

Of course, if they can’t afford, then bring on the description of how the poison is coursing through their veins, have it flavor your description of the result of injury rolls and so on.

Damage types

Damage types aren’t ‘messy’ attacks either. It’s just that if you are immune to “slashing” then it’s free to defend against those attacks, and if you are vulnerable to “slashing” it costs double. Just because the damage has a type doesn’t mean that they need to connect for the type to be relevant. Superman reacts differently to bullets than to kryptonite, even if the bullets are whiffing.

What Is Messy?

Anything that has an “on-hit” effect beyond just HP loss is ‘messy’. Paralyzation, stirge-attachment, grappling…

There is no second line of defense against ‘messy’ attacks; you can’t spend HP to avoid them. You just get a wound and the effect, such as being grappled, having a stirge drinking your blood, being infested by rot grubs etc.

DMs, take note of how much HP it would’ve cost because that’s what they’re gonna spend once they do somehing else, such as defend from other attacks, or try to break free.

You can also charge them upcoming turn’s actions in advance (if you are able to keep track of that).

Some examples of ‘messy’ attacks:

Ghoul Paralyzation

The rulebook says:

Claws: Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 7 (2d4 + 2) slashing damage. If the target is a creature other than an elf or Undead, it must succeed on a DC 10 Constitution saving throw or be Paralyzed for 1 minute. The target can repeat the saving throw at the end of each of its turns, Ending the Effect on itself on a success.

So, after failing the first line of defense, we:

— “The ghoul tries to rend you with its filthy claws!”
— “I try to yank my arm away!”
— “OK, make a DC 10 con save to do that.”
— “I failed the save.”
— “OK, take a wound as the claw finds a weak spot in your armor and tears your arm. You feel your body stiffen up and you can’t move.”

(DM notes a 2d4+2 debt to be charged on a later action, which might be lethal.)

Crocodile Grappling

The rulebook says:

Bite: Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 21 (3d10 + 5) piercing damage, and the target is Grappled (escape DC 16). Until this grapple ends, the target is Restrained, and the Crocodile can’t bite another target.

After failing the first line of defense:

— “Bob, the crocodile is snapping its jaws around your leg! You’re bleeding, take a wound!(Turns to Alice) Alice, what do you do?”

(On a later turn)

— “I try to yank my leg free!”
— “Pay 3d10+5 and make a strexterity check to do that.”
— “Did you say ‘strexterity’?”
— “Yeah, your choice of strength or dexterity.”

(DM can rack up 3d10+5 for every turn Bob is grappled and charge them all before the check when he tries to yank loose.)

Rot Grub Infestation

Rulebook says:

Bites. Melee Weapon Attack: +0 to hit, reach 0 ft., one creature in the swarm’s space. Hit: The target is infested by 1d4 rot grubs. At the start of each of the target’s turns, the target takes 1d6 piercing damage per rot grub infesting it. Applying fire to the bite wound before the end of the target’s next turn deals 1 fire damage to the target and kills these rot grubs. After this time, these rot grubs are too far under the skin to be burned. If a target infested by rot grubs ends its turn with 0 hit points, it dies as the rot grubs burrow into its heart and kill it. Any effect that cures disease kills all rot grubs infesting the target.

After failing the first line of defense:

— “You are infested by 1d4 of these maggots.”
— “Ah, I rolled a three! Three maggots are inside me I don’t know what to do! I try to roll around on the ground!”
— “OK, pay 3d6 HP to do that. The rot grubs aren’t affected, they just burrow in deeper.”

The DM notes 1d6 per rot grub at the start of each of the target’s turns. All those dice are rolled once the target does something, or when they get rid of them by burning them away or receiving healing magic.

The Golden Opportunity

If the monster can’t pay, describe it as a golden opportunity, a weakness, “you see an opening”.

The player character can describe their killing blow.

Of course, non-lethal attacks are sometimes possible.

Charging Spells

This is all well and good for the clang-clang-clang-chop of chanbara or matinée films, but how about spells, especially cantrips? What about an Eldritch Blast or a Firebolt?

For some spells, we’ve taken to describe it as charging up the spell, or “reaching” for the spell trying to puuulll it out from the arcane realm.

This could also be fiddling with components. In the comic book The High Cost of Living there’s a scene where the witch brings out a twig, snaps it, and her enemy’s leg breaks. Perfect for Eldritch Blast. Describe your “misses” (including paid-for attacks) as taking out the twig, inscribing on it, chanting over it, and then, in the golden opportunity, snap!

I’ve done firebolts as slow chanting, enscribing glowing sigils in the air in front of me, as “You feel your blood is getting warmer”, bringing it up to a boil, ending in spontaneous combustion to ashes.

This also works for carefully and deliberately [aiming a bow] for that perfect shot.