Death's Door (3.5e Spell)

This spell halts a creature on the brink of death. While the spell lasts, the target can survive with up to –20 hit points, instead of the usual –10. In addition, the target automatically becomes conscious and disabled (rather than dying and unconscious) if reduced to negative hit points. If the target of this spell is normally destroyed before this threshold (if they are undead, for example), they gain the ability to survive at negative hit points while the spell is in effect.

Death’s door does not heal a creature, so a subject at or below –10 hit points (or below 0 hit points in the case of constructs or undead) when the spell ends dies.