Health

Health determines how much health a character has, and thereby, how much damage they can take. When a character is lethally damaged, they lose health; when a character resting they regain health.

Zero Health and Death's Door

There many ways to arrive at Death’s Door; when a character drops or is reduced to zero health, but is above a negative value equal to half their health, they are on a Status Effect referred to as Death's Door. To be on Death’s Door a player character either:

1. Drops to zero Health
2. Is suffering from a single status effect causing them to be on Death’s Door--like Exhaustion. Death’s Door effect is removed if the status effect is removed or reduced, or if the health is healed to at least 1.

If a character meets both of these criteria at any time, that character dies. Additionally, if a character goes past negative half their health, the character dies. If a character is suffering from two status effects that would put them on death’s door, the character dies.

Staying Alive

While the character is on Death’s Door, the player character makes a Luck save every round they are on Death’s Door at the every beginning of the round (or at least the beginning of their turn, if they forget):
On crit pass, they either have the status effect that brings them to Death's Door alleviated by one level, or they gain 1 health; on pass, nothing happens; on half-pass, the character survives but is stunned until the beginning of their next turn; on fail, they fall prone and unconcsious until the start of their next turn; on a crit fail, the character falls unconscious and will die on their next turn if they do not receive aid.

Character Death

GMs and players, Character Death can be a very emotional experience for the player involved and other characters involved. It is important to recognize this and to allow for some grieving if the player wants to grieve.
However, at the end of the day, this is a game and a collaborative game. The longer a player remains out of the game, the less fun they will be able to have, even vicariously.
Rather than rules, I have recommendations:

Ritualize the Death. Out of the game, Retire the die or dice that killed your character and give them a nickname. Tear up your character sheet; or bury it; or burn it; or put it in a folder and forget about it. In game, either right in the middle of the scenario where your character died, or right after, have a small funeral. Every player must say something good about your character. As part of the age of heroes, all heroes--deeds and death--are chronicled to be passed on as both a cautionary and an inspiring tale to budding heroes. The new character is someone inspired by these stories.
Storm Hell. GM, if you are willing, have your table, if they are unable to resurrect the character, go on a crazy adventure to rescue the dead character from the afterlife (Hell, Heaven, Limbo, Purgatory, Anywhere).

Get right back in the Action. Have a character sheet ready with your second character, or write “Jr.” on your character sheet and have your son/daughter/child come to avenge your death right at that same moment.
Deus Ex. Yes, your character just dies but, GM willing, maybe a God is willing to bring you back right on the spot to get you right back in the action. There is a bargain, of course, nothing in life nor death is free, but should you agree to it, your character is brought back, seemingly inexplicable. You bear the mark of your bargain, and your days are numbered.

Using Corruption

As noted in Corruption: By a player willingly choosing and taking a point of corruption, a player character can regain all health, remove all energy debt and regain full energy, remove all status effects, and regain all resolve die. This is a free action, does not cost energy, and therefore can be done at anytime. -- GMs, this is a powerful tool, can disincline a party to rest, and can make any after-scenario rewards pale in comparison, but bear in mind that Corruption is near incurable. Narratively, it is an occupational hazard of all adventurers.