A kaiju from the Ultra Series, subtitled the “Skull Monster,” debuting in the original Ultraman. They are often monstrous and ferocious but dim-witted in nature, and they also have a strong sense of camaraderie among their own kind. Contrary to their name, their body color is rarely red (inspiring Ultraman: The Ultimate Hero to have an actual red Red King, with the original yellow being used for females). They've appeared in The☆Ultraman, Ultraman 80, Ultraman Max (where they are subtitled the Armored Monster, and capable of shooting explosive rocks from their mouths like cannonballs), Ultraman Mebius, and more.
