Cthulhu from "Monster Island Buddies"
Cthulhu is a cosmic entity and one of the Old Gods, the first of The Dark Ones. Cthulhu is describe as a giant being with a squid-like face, bat-like wings and claws. Many years ago in ages long past, Cthulhu try to destroy the Multiverse cause of his hatred for all life. He would've succeed haven't The Council of Light stopped him. Cthulhu was then imprisoned in the underwater city of R'lyeh where he sleeps for all eternity. According to legend, if Cthulhu breaks free from his prison, it's the beginning of the end of the Multiverse. But over-time, Cthulhu became a myth and a fairy tale to scare bad kids and is long forgotten.
Trivia:
- Cthulhu will appear in Sunset Shimmer's Adventures of Equestria Girls: Legend of Everfree, where he is released from the Wondercolt Statue along with Bill Cipher after Midnight destroyed it during battle from Twilight and Sunset's Adventures of Equestria Girls: Friendship Games.