Dark Materia is a homunculus made by Dr. Stankfoot from a combination of Dark Matter and pure Zevo Compound to keep him company. She is not technically a mutant. Dark Materia has control over Dark Energy views Stankfoot as an incompetent fool and had always a deep hatred for the mad scientist.
Even though she was created by Stankfoot, she resents being controlled by him and actively schisms to be rid of him. The only thing keeping her from succeeding, is the intervention by Stankfoot's more loyal henchman Blacktop. She wanted nothing more than to kill him and take control of all that she sees.
In "Mutation Termination", She is killed by Stankfoot.