Chain?

From left to right:
Undertale: karmas a b1#ch (the censorship is part of the name*)
Insanity sans (former time trio phase 3)
Last breath
Betrayer
Dust (former time trio phase 3)
Ainavol

Background from left to right
Floating papyrus head
Gaster
Betrayer blasters
Phantom papyrus

*undertale: betrayer

So it's (from left to right):
Insanity sans
Last breath
Dustdust/ultradust (they are different things but I can't remember the diffrecnce)

(Undertale turns into bullet hell)

This looks cool

its not even worth fighting anymore at this point