BillCipher

"It's funny how dumb you are!"
Gravity Falls Spoilers!

This guy... is Bill Cipher from Gravity Falls. Yup, the chaotic triangle himself.
Hopefully, you know who Bill Cipher is, yet, if you don't, I guess you're going to.
He's a being of chaos, and usually takes the form of a triangle. In the show, he liked messing around with the Pines family, along with a town called "Gravity Falls". He ATTEMPTED to 'have an eternal party' by throwing the world into chaos but wasn't able to surpass the weirdness barrier around Gravity Falls.

This guy was thrown into a different dimension after defeat, taking the form of this dragon. He was confused at first since he wasn't able to use his normal chaos powers... but this lair was the first one he happened to stumble upon. They help him with showing him what's normal here, though that doesn't stop Bill from sticking to his chaotic nature.

His favorite elements are Light and Shadow, along with the holidays. Of course his favorites interfere, he was a being of pure chaos after all. His second favorite elements and their corresponding holidays are Ice and Fire. Once again, they of course interfere. He was originally hatched as an Ice element but switched to the Fire lair for a bit, then Light (which was the shortest one), then finally settled down with Shadow.