Tyrannus, also known as Casper Clayton, is a Marvel Comics villain, and an enemy of the Hulk.
Romulus Augustus was the last Roman emperor. Tyrannus believes that he was born to rule all. Thousands of years ago, Tyrannus composed a giant army to defeat King Arthur and conquer all of England. Tyrannus' invasion failed and he was banished into the world of Subterranea by Merlin the Magician. There, Tyrannus managed to find a colony of Subterraneans. Though some had lost the ability to speak through breeding, Tyrannus still felt that although they were not regular people they were still people to be lead. Tyrannus managed to find the Fountain of Youth and drank it to become immortal.