The attribute "Essential" can be assigned to non-player characters in games which use the Gamebryo engine, including Fallout 3, Fallout: New Vegas, and Fallout 4. The equivalent attribute for items is quest item, which should not be confused with the general usage of that term.
The main effect of this attribute is that the character cannot be killed, instead it will be temporarily rendered unconscious and wake up again later. In all games, all children in the game are essential characters, so even if a way to attack them is found, they still cannot die.
The purpose of this attribute is to prevent the player character from rendering quests incompletable by killing characters who are necessary for that quest. However, there are still characters involved in quests that can be killed. Upon their death, a notification will pop up saying that the quest they were involved in has been failed. However, the failed quest will not be crossed out in the Quests screen.
In Fallout: New Vegas, there are few essential NPCs aside from children, one of which is the robot Victor, who is essential early on in the game. The message "Victor is unconscious" may appear later in the game. All Companions are essential (unless playing Hardcore mode). Yes Man is also one of the very few essential characters, except for the fact that he could be viewed as just "respawning."
PC Fallout: New Vegas: random creatures may be tagged as essential, particularly golden geckos and creatures in their vicinity, effectively making them unstoppable.
- ↑ Quoting Emil Pagliarulo, "We don't want to cross lines like killing kids (we actually never got as far as even putting kill-able kids in any builds of the game)... For us, that was a line we certainly didn't want to cross, and we think that was the right decision. It wouldn't have been socially responsible, at least in the case of Fallout 3."