Here is the full list of all 23 Afterparty achievements.
Intentionally lose to Satan.
Pet the damn dog.
Try 20 different drink types.
Recruit the Drunk Idiot Demon for Satan's final challenge.
Make friends with Sam.
Make friends with Wormhorn.
Reunite Milo and Lola.
Play as Milo after fighting with Lola.
Waste 20 minutes on Bicker.
Get Apollyon's Seal of Approval.
Intentionally curse twenty times.
Get Asmodeus's Seal of Approval.
Get an Invite to Satan's from Lynda.
Don't miss a step while dancing.
Kick off your adventure in Hell.
Get an Invite to Satan's from Fela.
Play as Lola after fighting with Milo.
Fail to beat Satan.
Beat Satan and earn your way back home.
Reunite Beth and Asmodeus.
Play a perfect game of beer pong.
Play a perfect stacking game.
Drink a lot of booze.