Once Bitten, Twice Die

 a limited-time questline released on October 30, 2019. It the main questline of Act 2 of the Treehouse of Horror XXX Event, following Operation Clogged Drain.

End
Unlocks Seven Sisters.

End
Unlocks Pumpkin House or gives 12 Donuts.

End
Unlocks Gingerbread House or gives 12 Donuts.

End
Unlocks Martin of the Opera.