Underfell

This story is about these 4 skeletons named Horror,Dust,Fell and Swapfell from different universes,but the problem is,there is a terrible persom, named Gaster, planning to destroy all the AU's,So he can make his own universe with the other destroyed AU's (Different Universes),So these 4 skeletons are trying to change all of this before it happens and their worlds are completely destroyed