If a non-marked enemy is killed, the skull will disappear and no bonuses will be granted for that room.
As long as the room is not cleared, Isaac can re-attempt a Death's List by leaving and re-entering.
The marked enemies are chosen in the same order in a given room, starting from the top-left corner with enemies that are vulnerable at their spawn time. If new enemies are spawned via Portals or on death, they are added to the end of the marked queue.
A room with no enemies that instead requires Silver Buttons to be pressed will also give a reward when cleared.
If a reward stat is chosen that is already at maximum, the sound effect and Isaac's thumbs up animation will play, but there is no other effect.
Bosses may also be marked.
If a Portal is marked and despawns, no other enemy will be marked and the bonus is lost.
In the Mom boss fight, each of Mom's body parts (eyes, foot, and hands) is considered as a different enemy, and Isaac has to kill the foot to get the bonus.
If the doors open automatically due to spending a long enough time in the room, any existing mark will disappear.
When playing as Tainted Jacob, Dark Esau can be marked by this item, and will be marked first if he is alive when you enter a room. This makes this item much less useful for Tainted Jacob.
Familiars, especially ones that passively or actively damage enemies of their own accord, may make killing enemies in order difficult, if not impossible.
Ace cards will kill the enemies in the correct order when possible.
If a Mr. Maw is marked, killing either part of its body will not forfeit Death's List, as the remaining enemy of said Mr. Maw will still be marked.
Flush!: When a room is cleared with Flush!, a bonus will be awarded.
Door Stop: If the player has failed Death's List but hasn't cleared the room, leaving and re-entering will reset the list.
Freezing attacks: Enemies that die by freezing do not disrupt the Death's List chain, though the shards caused by them breaking do.
Toxic Shock: Not recommended. If multiple enemies are killed by Toxic Shock at the same time, the mark will disappear and no reward will be given, even if the enemy next in line to be marked was killed at the same time as the marked one.
Death's List was added in Booster Pack #4, after the initial release of the DLC.