He is a character from "My Little Pony: Friendship is Magic".

King Sombra played General Grievous in Dragon Wars
King Sombra Played Soto In Animal Age
King Sombra Played Kazar in The Wild (Davidchannel's Version)
King Sombra played Gallaxhar in Dragons vs Changelings
King Sombra played The Hydra in Godzillacules
King Sombra played Galactus in G4 Ponies vs G3 Ponies 3/Ultimate
King Sombra played Nightmare in Steven Universe: Right Back at Ya.
King Sombra played Butler in Twilight Sparkle and the Ghostly Adventures and Apple Bloom and the Ghostly Adventures
He is a ghost