Morloo was the supernatural ally of Doctor-7, an evil sorcerer and arch-enemy of the mystic sleuth, Mark Merlin.
Originally, Morloo was a being from the 14th Century, however, in the 20th Century, an alchemist named Thandor, and his assistant Herxa, were able to conjure up Morloo and release him onto the world. By using his magical powers, and creating a formula with Radium, Doctor-7 was able to control the creature and make him his own "supernatural ally."[1]
The Morloo was able to remain on Earth due to the Doctor's secret potions, but the results were only temporary. Eventually, Mark Merlin was able to uncover the "secret code" to the potion in order to send Morloo back to his original world and trapping him there forever.[2]
This version of Morloo (Earth-One), including all history and corresponding appearances, was erased from existence following the collapse of the Multiverse in the 1985-86 Crisis on Infinite Earths limited series and is now considered apocryphal.