The party is going well! People are enjoying the music and dancing, socializing, and generally vibing, when about halfway through some prankster casts a spell!

It was supposed to just be a harmless prank, and a fairly clever bit of magic as well, taking the idea of the costume and making it More, transforming everyone into their costume for an hour at most. But something got hold of the spell and twisted it to last a lot longer!

This obviously puts a damper on the party itself for most people, but some people shrug and continue on like nothing was out of place too!

Afterwards everyone needs to be transformed back manually. Easily done for most people, with the more extreme and dangerous transformations taken care of that night at the party, and most of them handled by the Mage Guild during the following week.

The characters at the party are transformed into the costume they're wearing. Werewolves, Vampires, Ghosts, Skeletons, Zombies, you name it! Characters gain the supernatural abilities and weaknesses of these things as well, Ghosts can fly and shift through walls but are mostly invisible, Werewolves are stronger faster and furry but are weak to silver, etc.

Reversal is easy for most people, and is taken care of quickly for the more dangerous or extreme changes, reversal happening that same night. Over the following week members of the Mage Guild will go around reversing the transformations that they can, according to need. The power of the spell itself depends on the affinity the character has to the transformation, without intervention the spell ends a variable amount of time, lasting approximately a week to a month, with some changes being permanent without stronger reversal magic being sought out.