A villain in the DC Universe. First appeared in Green Lantern #10.
Many, many years ago (say, 50,000 or so) there was a tribe of cro-magnons led by their cheiftan, Vandar Adg. Rip Hunter, knowing that a cro-magnon named Vandar Adg would one day become an immortal super-villain, journeyed to this time and killed him (obviously not troubled by that old conundrum). Vandar's son then assumed his name and became the new cheiftan, and Rip Hunter realised he'd killed the wrong Vandar Adg.
Later, while Vandar Adg was fighting another cro-magnon named Klarn, a fiery meteor fell nearby, bathing them both in some strange radiation. Vandar gained immortality, while Klarn was to reincarnate again and again to oppose Vandar as the Immortal Man.
Vandar has spent his immortal life gathering knowledge and power. He has ruled openly (ruling Egypt as the Pharaoh Khafre and, he claims, Rome as Julius Ceasar and the Monguls as Khengis Khan) and behind the scenes (advising Napoleon and Bismarck). Sometimes he prefers merely to influence events through the Illuminati, a society he created and leads. He has access to both great technology and great magic, and may use either to further his aims.
In the age of superheroes he is known as Vandal Savage, and has faced a great many heroes and teams. He has battled the Justice Society of America, and was a founding member of the Injustice Society of the World. He has faced all three Flashes, almost killing Wally West in the early years of his career as the Flash. He has also clashed with the Justice League Task Force and the Titans (the latter as the leader of Tartarus, another group of supervillains).
He is known to have survived into the 853rd century, where he planned to merge with the artificial sun Solaris, but he was foiled by the Justice League and Justice Legion A.