The fact that her aunt will off her if she doesn't have the orgytastic sex is maybe the best part. That plus the dialogue between Merry and her aunt is hilariously predictable.

Aunt: blah blah threatening cakes.
Merry: sullen apology, Aunt.
Aunt: It is funny how you can say that and still sound like you are saying Fuck Off and Die.
Merry: ...sullen apology, Auntie.
Aunt: Still with the fucking off.
Merry: OMG U R TEH DEVIL!
Aunt: Sweetie, I will totally have incestuous sadistic lesbian sex with you if I thought it would give me the magical power to light a candle.
Merry: ...my bad.
Aunt: Go fuck a guard. Or five.