Prologue- Whats this? A crossover episode!?

The barrier has been broken. Not due to SOULs, but due to a successful experiment by Doctor Gaster. Now, monsters must assimilate into the human world, where, apparently, the mages are in hiding. Hogwarts school is always a safe place from outside politics, but how will it adapt with literal monsters in its walls?
Featuring Sans as the main character! (Multiple POVs at certain points, and maybe a few chapters with a different main character?)