emperor belos

Warning, heavy spoilers ahead, don't click on them, if you didn't watch the whole cartoon including the episode "King's Tide"!

The main antagonist of the cartoon The Owl House; He rules the Boiling Isles with an iron fist and is actually the human witch hunter Philip Wittebane, who came to the Boiling Isles from the human world in the 1660s and became the Isles' ruler to destroy all witches and demons.
He was seemingly killed by The Collector, but the globs of green goop that were left of him seem to be alive somehow and hitched a ride to the human realm.