Mephistopheles is an unused character who would have appeared in a changing portrait in the Haunted Mansion.
The Devil appeared in a piece of Marc Davis concept art for the Haunted Mansion's Changing Portrait collection. He would have appeared behind an old miser after the old man would have burned to nothing, the devil would have held a contract reading "Sold" alluding towards the old man having sold his soul to the devil (likely for money) and that he was spirited away to Hell.
Mephistopheles is a demon from German Legend and Abrahamic Folklore who is an agent of the Devil, Lucifer and who has the task of retrieving mortal souls which belong to the Devil. He originates from the legend of Faust where he buys the soul of the titular scholar Johann Faust and spirits him away to Hell in order to bring Faust's soul to his boss, the Devil. Mephistopheles' soul is also said to be owned by Lucifer.
- You can tell that the figure is meant to portray the archetypal Mephistopheles devil rather then the archetypal Satan one based on the clothing he wears being renaissance inspired, a trait specifically used for the Mephistopheles figure although in certain stories the two are portrayed as one character.