Blood Sigils are checkpoints to be found while adventuring in Gehenna.
When a character dies, they are indefinitely out of the game until the rest of the party reaches a new Blood Sigil, or return to their last one. For respawning, they lose 1 Composure.
When a character dies while having no composure, the character is permanently dead. You may choose as you see fit with what to do for that character, whether they mutate into a Demon, lose their mind, or disappear.