Amethyst is a partially robotic wolf, who serves Desmond as an Artificial Companion Unit. She's basically a substitute wife or girlfriend for him.

Amethyst used to live a normal life, with a husband and a daughter of her own, but Desmond took their lives, and revived Amethyst using robotic parts to become one of his faithful servants. Most of her memories were wiped, but some of them are slowly returning to her. Unfortunately for Amethyst, like the other robots she cannot leave the cave or escape Desmond's control, or else she will be scrapped and destroyed.