Note: This page is taken from n.wikia.com.
Undeath is a situation that can occur in N in some of the more devious levels. Basically, undeath is when the ninja is unable to go anywhere or solve the level in any way. This can happen if the ninja is trapped in a cell with a trap door blocking the only way in, a trap door blocks the way to the exit, or an enemy such as a zap drone or a floorguard gets into a position where it blocks the ninja. If the player gets into a situation with undeath, their only option is to kill themselves and do the level again.