Mephistopheles is a woman adorned in Rogue's clothes and a gold mask. She wields a parrying dagger and epee rapier. Once Yurt is dead and the player has pure black character tendency, she can be found in Yurt's old spot on the second floor of the Nexus.
She is a high ranking member of Soul Industry, a masked society of individuals who wish to keep the secrets of the Soul Arts for themselves. She employed the mercenary Yurt the Silent Chief to murder all those in Boletaria who have knowledge of the Soul Arts. If the player has pure black character tendency and has defeated Yurt she offers to employ them to finish the job. If the player takes her up on her offer and fulfills all of her contracts, she will then turn on the player and attempt to kill them because they are the last non-member with knowledge of the Soul Arts.
Though an epee rapier has a blunted blade and is typically used in fencing contests, the epee rapiers wielded by the Soul Industry are imbued with a strong magical flame. Thus, strikes by the epee rapier only lightly cut the flesh, but horribly burn it as well. This example of viciousness is one of the reasons the Soul Industry is so feared.