D is for Doctor Fate

Doctor Fate (along with his wife Inza) appears in the Justice League episode "The Terror Beyond" voiced by Oded Fehr while Inza is voiced by Jennifer Hale. Dr. Fate and Aquaman help Solomon Grundy escape from the authorities so they can enact an age-old spell to save this dimension from an invasion by the Old Ones, creatures based on the writings of H. P. Lovecraft.

The Justice League animated series Doctor Fate is apparently based on the Kent Nelson version. He was the son of American archaeologist Sven Nelson. When his father opened the tomb of the wizard Nabu, a poison gas was released which ultimately resulted in the death of Sven Nelson. Nabu took pity on the orphaned Kent. The wizard raised him and taught him the skills of a wizard, then bestowed upon him a mystical helm and amulet.

Nelson returned to the United States and resided in an invisible tower in Salem, Massachusetts. From this sanctum he embarked on a career fighting crime and supernatural evil as the hero, Doctor Fate.

I don't really know much about Doctor Fate. Just not into the occult, magic or sorcery stuff. I much prefer the physical action scenes and sequences. Guess I'm just that kind of a guy.

Marvel comics equivalent of such a character would be Doctor Strange, co-created by writer Stan Lee and artist Steve Ditko, and first appeared in Strange Tales #110 (July 1963).

There always seem to be a parallel character in both DC and Marvel. In the case of Aquaman, there's Namor the Sub-Mariner from Marvel comics. For Clayface, there's Sandman from the Marvel Spiderman comics.