In her mist form, ERROR_ appears as a black mist, almost flame like. It also has 2 red eyes if you look closely. In her humanoid form, ERROR_ appears as a black robloxian with two horns, a female torso and red eyes. She is devoid of any other features.
ERROR_ is a very prominent character in the series, especially when she’s the main antagonist.
ERROR_ was originally a part of Subject_0, but then gained sentience.
She is the cause of Subject_2 being corrupted into a monster.