The Demands of the Mistress Ending is an Ending in Prisoners of the Elder One. It occurs after leaving the mansion through the front door if Tiffany was rescued, but is still a catslave.
Erik and Tiffany are transported into a fancy bedroom, and are transformed into a dominatrix and a submissive, respectively. Erik soon gets memories of being Alice, a domme heiress with the powers of telepathy. She spends the rest of her life gaining power with her telepathy and controlling what was once her sister.