I’ve done a similar combat system to this one in the past, so consider this a revision or just forget the last one.
Once again, I’m thinking in terms of a deadly combat system, more realistic perhaps than the traditional hit points/armor class system, and potentially over quickly.
The system is written for Blood & Treasure, but should be easy to adapt. It assumes you are using the combat advantage system in Blood & Treasure. It works as follows:
A. Each character makes an attack roll, add half armor class bonus from natural armor or worn or carried armor (i.e. shields) to this roll
B. Compare the attack rolls – high roll wins the combat round
B1. If a combatant rolls a natural ’20’, their opponent is either killed or, if they are merciful, knocked unconscious or left prone and disarmed (and dishonored)
B2. If a combatant rolls a natural ‘1’, they suffer a catastrophe – roll 1d6
1. Disarmed (must draw another weapon or fight unarmed)
2. Trip or slip (fall prone, Reflex save or lose weapon as well)
3. Backed into corner (opponent gets an advantage, as you cannot maneuver)
4. Face cut (blood in your eyes, opponent gets an advantage)
5. Hand cut (must fight with other hand, giving opponent an advantage unless you are ambidextrous)
6. Roll again (or if anyone has another good idea for a catastrophe, let me know!)
B3. The loser must pass a Fortitude saving throw or is fatigued, suffering the normal penalty to attack rolls, but also extending their fumble range by 1 (i.e. from 1 on 1d20 to 1-2 on 1d20, etc.) A combatant with armor must take a penalty on this save equal to half their armor class bonus.
B4. The winner need only make a Fortitude save vs. fatigue in even rounds of combat. Each round that they win, they increase their critical threat range by 1 (i.e. from 20 on 1d20 to 19-20 on 1d20, etc.)
C. Keep rolling combat rounds until somebody is dead (or unconscious) or surrenders
Multiple Opponents – the outnumbered foe has to roll against each attacker, all of whom derive a combat advantage from the situation, and might have to make multiple saves against fatigue. Only the attacker’s first attack roll counts against a chosen opponent in terms of causing fatigue or death. Unlike with normal rules, heroes sallying forth against multiple foes are probably doomed unless they well out-level them.
Multiple Attacks – Monsters or characters with multiple attacks make those attacks as normal, with each defender making their own attack roll against them, or a defender making multiple rolls against them; as above, only the character’s first attack roll counts towards causing fatigue or death.
Missile Combat – This system doesn’t work for missile weapons, but consider this idea: Make attack rolls against AC as normal. Roll the hit location (you can devise your own table) with that body part being made useless unless the struck character passes a Reflex save. Obviously, hit locations like head, throat or heart would carry with them instant death.
Other Sources of Hit Point Damage: To get rid of hit points, you’d need to deal with things like fire breath or falls. If you like things to be super dangerous, you could always go save or die – or perhaps save vs. being crippled, severely burned (you’d have to determine just what that entails), frostbitten, etc. with a roll of “1” indicating that the attack killed you outright.
Impact of System
A system like this opens some interesting possibilities. High level characters are still hard to kill, but maybe not as hard as before – even a first level character can get lucky against a high level character with a system like this in a way that is essentially impossible using traditional combat. Likewise, first level characters are going to have a tough time surviving, but might actually last many more rounds than they would using the traditional system.
If you try this system out, let me know how it worked.