Weirdmageddon Again (Billdip)

What if later on in the future like when the twins are 20, weirdmageddon happens again but this time it's different? What if Dipper offered Bill a deal that bill couldn't resist? Who would save the town if the Pines Twins were separated? Who would stop Bill if Stan and Ford's trick didn't work this time? Read to find out what happens.
I would like to put a few warnings on this real quick. Smut, bad language, and some violence.