Plot character

A plot character is an NPC who is involved in scripted plot points, and who the game developers have therefore made unkillable, in order to prevent the game from breaking. This is a common device in role-playing games.

This may by implemented by automatically reviving the NPC shortly after death (such as Dogmeat from Fallout 4), or the NPC may simply never die.

Plot characters may become killable once they have served their role in the plot.

Since it is so obviously artificial, this mechanic tends to disrupt suspension of disbelief. In some games, it can even be exploited to some degree. However, it's often a necessary design consequence of a scripted narrative.

Mechanically, plot characters are closely related to plot items.