SetEssential

Syntax:

SetEssential ActorBase bool 

Example:

SetEssential MyFavoriteNPC 1
SetEssential MyLeastFavoriteNPC 0

Sets the "essential" flag on an actor (1 or 0). When this flag is set to 1, the NPC/creature will not be killable -- when his health drops to 0 or below, an essential actor will be made temporary "unconscious". This is normally used to prevent the player from accidentally killing an NPC who is required to complete a quest.