The Graeae in Perseus and Medusa
The Graeae are the three old, unhygienic sisters who share an eye and tooth. (All together now: eewwwww!) These supernatural ladies know the location of the Nymphai, who possess the supernatural tools that Perseus needs to kill Medusa. The Graeae don't want to help Perseus, but he steals their precious eye and tooth and refuses to return them unless the Graeae spill the beans. Perseus is one persuasive guy.