A descendent of original vault dwellers, the survivor has been left insane by the psychoactive drugs that are still being pumped through the air systems of Vault 106 as a result of the vault's experiment. Because of this, the survivor only functions on primal reflexes.
The survivor is always hostile to the Lone Wanderer.
When the survivor's health is reduced below 80%, a hallucination starts in which the survivor disappears and the Lone Wanderer is attacked by hallucinatory versions of their childhood bullies, Butch DeLoria, Wally Mack, and Paul Hannon Jr.
When the survivor's Hit Points are reduced below 45%, a hallucination starts in which the survivor turns invisible (the same as a Stealth Boy effect), causing the Lone Wanderer to miss most shots taken in V.A.T.S.
If the survivor is killed immediately when encountered, the childhood bully hallucination and Stealth Boy effect may not occur.
Alternatively if the Lone Wanderer companion kills him/her, nothing will occur until at least one hit is made by the player character.