(Endorsement) Contracting Mephisto

Lore
"Time has been reversed, restoring your youth." Mephisto's improbable feat secured the man's soul as dictated by their agreement. But so as not to utterly crush the spirit of her prey, she would offer a single escape clause: they would be granted freedom if they uncovered her true identity.

Acquisition
See Contracting Mephisto

Name origin
Mephisto is a character from Johann Wolfgang von Goethe's tragic play Faust.