Tyrannosarus rex. Grateful, the old man gives Tor a club which possesses great powers. Tor raises the club and he becomes Mightor, and Tog is transferred into a fire-breathing dragon. Together they become champions of good and the nemesis of evil!" From the opening narration. link.
Mighty Mightor debuted this day in 1967 as part of the Moby Dick and Mighty Mightor Hanna-Barbera cartoon show.