Howdy Shields! I wanted to make getting dropped to 0 HP Fun, so I made a pair of charts. One identifies how hurt the PC becomes, and whether they live or die. The other identifies something awesome you can do thanks to being so grievously injured. Full disclosure: I haven’t used these rules in a game yet, so let me know how they go.
Directions
Once a player character is reduced to 0 HP, rolls are made on the tables below. The rolls are not modified by damage or stats, but the Banes of Combat is modified by a cumulative -5 each time it is rolled on for the same PC in the same combat. Players may spend hero tokens or surge dice (insert favorite metacurrency here) to modify the rolls. Roll once on the Banes of Combat table, and once on the Boons of Adversity table.
Banes of Combat
-4 and below - Inglorious Demise - PC has suffered an immediately fatal blow. Do not roll on the Boons of Adversity table.
-3 to 1 - Glorious Death - PC has suffered a grave injury, and will die after their next action, but until then, all their stats but luck are restored to full, and their next action receives a +20 bonus to succeed, and all result rolls of that action are advantaged, or in the case of damage rolls, treated as critical, in addition to whatever boon is rolled.
2-3 Maimed - limb is harmed; roll 1d3 to determine whether main arm, off arm, or leg. Actions made which use the injured limb are at disadvantage. Each round that the PC uses the injured limb, they must make a save v. losing the limb at the end of the round, and begin bleeding out.
4-5 Pinned - PC in pinned down or trapped under or on something. The PC can break free, but will suffer disadvantage to all attacks, become slowed, and begin bleeding.
6-7 Busted - injury in the ribs; PC must make a save at the start of each round they choose to do anything but tend to their wounds. If failed the PC is slowed, and suffers disadvantage on attack and damage rolls for that turn. If the PC fails 3 such saves, the PC falls unconscious, and begins bleeding out.
8-9 Skewered - something is now sticking out of the PC, imposing disadvantage on all attacks and spell casting. The PC can pull it out, but doing so starts the PC bleeding out, and risks a permanent -2 to str, dex, or con.
10-11 Bloodied - The PC has suffered an injury causing significant blood loss. If left untreated, the PC will be dead by sunset/sunrise, falling unconscious one hour before. Every round the PC continues fighting, they make a fort save. If failed the PC begins bleeding out, meaning all actions and damage rolls are at disadvantage, and the PC becomes slowed and weakened. Every round after beginning to bleed out the PC makes a fort save to remain conscious at the end of their turn which increases in difficulty every turn. Every round they remain conscious, the PC suffers a level of fatigue (-1 to str and dex bonuses). After passing out, the PC will die of blood loss in 1d2+con bonus rounds.
12-13 Clobbered - head wound; PC saves vs being knocked prone and dropping whatever was being held. Every round the PC does anything other than tend their wounds, they must make a save at the start of the round. If failed, the PC gains the "confused" tag, and suffers disadvantage on all actions that turn. At the end of the scene, the PC must make a save based on the number of rounds they acted without getting treatment; if failed, the PC permanently loses either 2 int, 2 cha, 2 wis, or some combination, and forgets a random spell for the day.
14-15 Cracked - an item in the PC’s possession has been damaged, and risks breaking if subject to further use. Every round of continued use forces the player to roll a save based on the amount of damage they suffered beyond 0, or the item breaks.
16-17 Winded - the PC has the wind knocked out of them. The PC saves vs dropping whatever was being held, and falling prone. The PC may catch their breath by resting a number of rounds equal to half the damage suffered below 0 (minimum 1). Continuing to act in any way that is physical or uses breath is made at disadvantage, including attacks and damage rolls. At the end of each round the PC does not rest, the PC makes a fort save v. suffering a level of fatigue (-1 to str and dex bonuses per level of fatigue). If the PC fails 3 such saves, they fall unconscious.
18-19 Laid out - PC is knocked flat on their back. The PC makes a save (DM’s prerogative) v. dropping whatever was being held. The PC may recover by lying prone for one round. If the PC chooses to get up, their actions and damage rolls are disadvantaged for one round, and they must make a fort save v. suffering a level of fatigue (-1 to str and dex bonuses).
20 Scarred - injury is cosmetic, creating a long scar, missing ear, severed finger, etc. If the PC refrains from further combat, nursing the injury instead, the wound will only mark the PC as a grizzled veteran of a violent lifestyle. However, if the PC continues on, they risk aggravating the wound, imposing a permanent -2 penalty on activities related to the injury. Every round the PC continues to fight, they make a fort save to resist aggravating the injury.
Boons of Adversity
1 Panic - The PC is overcome with a sense of urgent panic. As long as the PC is acting to escape the fight by the safest or shortest route available, they can escape any grasp, bond, or snare, and may ignore the effects of their injury. While moving to escape, the PC gains a bonus to avoid harm equal to the damage suffered below 0. Once the PC stops trying to escape, or the DM determines that they have escaped, these bonuses end.
2-3 Blind Rage - The PC is overcome with white-hot rage. The PC may defer the effects of their injury for the duration of the rage, and gain advantage to all attacks, damage rolls, and tests involving str or con as long as the PC is attacking or acting aggressively against their opponents. The rage ends when all the enemies have been defeated or fled the field, or in a number of rounds equal to damage suffered below 0. The PC can choose to end the rage early. Once ended, the PC suffers all the deferred effects of their injuries at once.
4-6 Playing Possum - the PC may use their injury or appearance of injury to draw their opponent into a trap. Once injured, the PC may defer the effects of their injuries, and lie in wait, tempting their opponent to finish them off with a cha test. When the opponent comes in range, the PC may interrupt their action with an advantaged attack, which if it hits is considered a critical hit with advantaged damage.
7-8 Sundering Riposte - the PC gets an immediate reaction against the source of their injury with advantage to all rolls and damage. If the attack succeeds, then the kind of attack that injured the PC is no longer available to the opponent.
9-10 Turn the Tables - the PC finds a way to turn their opponent’s advantage into a liability. The PC may choose one action of the opponent that injured them. The PC may now either cause the effects of that action to affect the opponent and their allies, or to have the reverse effect on the PC and their allies. The DM is asked to apply their best judgement and common sense as to how this works mechanically, and how long it lasts.
11-13 Grim Determination - The PC is filled with an indomitable will to see their task done. The PC chooses a goal which is achievable in about 5 rounds, which is not the pursuit of the PC’s healing or escape. Once selected, the PC may defer the effects of their injuries until that task is completed, and all actions taken in pursuit of the PC’s goal gain advantage. Once the goal is completed, the PC suffers the effects of each round of their injuries at once.
14-16 Heroic Surge - The direness of the PC’s injuries drive them forward with alacrity and focus they did not know they possessed. The PC gets two full actions this round, both at advantage for tests and results. The PC also gets to defer the effects of their injuries until the following round.
17-18 Glimpse Behind the Veil - The PC’s injuries bring them a moment of clarity in which the way to perform a complex action is revealed to them. The PC unlocks a new spell or ability which they can use at advantage on their next turn, ignoring for that action any penalties imposed upon them by their injuries.
19 - Divine Intercession - the PC’s becomes the conduit of divine will, making the impossible possible. A deity connected to the PC makes known to them their will, and allows the PC to ignore the effects of their injuries until their divine task is completed. The PC may also interrupt any opponent interfering with the completion of this task with a one round stun. If the PC delays attempting to complete their appointed task for any reason, all benefits of the intercession are lost. Once the task is complete, or the intercession is lost, the PC begins suffering the effects of their injuries as normal.
20 - Revelation - injury has revealed in the mind of the PC a powerful and actionable truth or weakness of their opponent, and gains advantage on all rolls to act on it. This may be a predictable weakness in the enemy’s technique, a gap in their armor, or the chandelier looming above them. It doesn’t even have to be about the opponent who injured the PC; it just has to be new information that the PC can act on to change the landscape of their current circumstances. Most critically, the PLAYER takes temporary and limited authorial control to tell a story about what the PC has realized, and how it changes the situation for their advantage.