I found myself in a Dungeon Crawl Classics session with a player anxious about character deaths, and a GM who struggled to process the actions of a dozen player characters simultaneously.
I was asked to create something that would make the game more accessible to the group. Something that gives more control over death without losing the sense of danger, and something that can make a dozen or more characters easy to handle.

After some careful consideration I came up with something that combines elements of Pokemon and Darkest Dungeon into something that we felt flows well in the context of a tabletop session.
The Active Character Technique (TACT)
No matter how many characters are at the scene of a battle, the number of Active Participants is limited to one character per player. Likewise the GM is also limited to one monster/opponent per player. All other characters are considered to be Passive – they remain in the background unable to participate for the moment.
Note: Minor NPC allies (Hirelings, battle-pets, etc) are considered characters belonging to the appropriate player for the purpose of these rules. Thus one player has a hunter with their loyal attack-dog, the hunter and dog are considered to be two separate characters.
Use the standard combat rules for initiative, turn order, and so on. The active participants fight using all the standard rules for attacking, casting spells, using items, and so on. However they are limited to targeting the other Active characters. The passive characters in the background may not be targeted by attacks, abilities, and so on.
In the event that a character is killed, incapacitated, or otherwise removed from combat they must be instantly replaced with another character from the player’s roster. Otherwise combat continues until one side is victorious as per the standard rules of your game.
On the player’s turn they may choose to Switch-Out their currently Active character. The currently active character fades into the background, and another character is thrown into the Active position. This uses up the player’s turn. Characters can be switched in and out of the active position as many times as the player wishes.
Another option is also available: When the player wishes to remove a character from danger right this instant, they may choose to Tap-Out. This removes the character from the combat, and they may not return to the fight. Such characters have fled the scene, collapsed from exhaustion, or whatever else might be appropriate. Since they have been “Removed From Combat” the player must instantly put a new character into the Active position.
Players may Tap-Out at any time, and are not limited to their own turn. The only restriction is that if an attack, ability, or other effect has targeted the character that action must be resolved before the player’s Tap-Out can go into effect. (Thus if a monster rolls a successful attack roll, the player cannot chose to tap-out their character to avoid the damage.)
The player may not “Tap-Out” their final character. Thus players should carefully consider the order they want their characters to participate, since the very last character might be in the greatest danger.
The ultimate fate of tapped-out characters is left to the GM’s narrative judgement. However the social contract of these rules should clearly be interpreted that a character who has tapped-out should not simply be killed. Adventure stories are full of scenarios where heroes run away, suffer permanent injuries, get captured, mugged, or simply left battered and bruised.
Status Effects & TACT
To reduce the mental burden of combat: All negative conditions like bleeding out, being poisoned (etc) are temporarily ignored while a character is Passive or has Tapped-Out. At the end of combat their conditions should immediately be addressed. Thus if a character is poisoned and the player taps them out, the poison has the decency to wait until after combat before attempting to kill the character.
This will obviously give the players the advantage when it comes to giving appropriate treatment to such conditions, but it also prevents the combat action from grinding to a halt as characters focus on stabilizing their allies instead of thwarting their foes.
A TACT-ful version of Death’s Door
When a character reaches zero hit points they are in mortal danger. They do not instantly die, and they cannot go into a negative hit point value.
This gives the players an opportunity to tap-out, surrender, or otherwise have some agency on if they are willing to risk their character’s life in this moment. Characters who have been Tapped-Out at zero hit points are considered to be bleeding out as per the normal rules for your game, however as per the TACT method they will not need to be bandaged up until after combat is over.
While at zero hit points any FURTHER damage has a chance to instantly kill the character. This life-or-death roll uses a d20, and the goal is to roll equal or below the character’s Stamina/Constitution score. If the roll is successful the character remains defiantly standing at zero hit points and continues to act as normal, however if the roll fails the character will perish.
If the death roll lands on a 1, the character recovers 1hp. However if the death roll lands on a 20, they will always perish regardless of their attribute score. This means that even characters with phenomenally high attributes are not immortal.
At the end of combat, any character that made a “Death’s Door” roll permanently loses one point of Stamina/Constitution.
Thorn-Image generated by Craiyon.com.