For the post-Crisis Lord Satanus click here:
The origins of the mysterious Lord Satanis remain unclear. He never reveals his name or removes his mask. He was born in the far future, more than a million years from now, at a time when magic had supplanted science. Earth was then ruled by the sorcerer Ambra, who possessed the mystic Runestone of Merlin. Satanis led a revolt of sorcerers and, with his magic, killed Ambra. However, with his waning power, the dying mage sent the Runestone through time to prevent Satanis from taking it for himself.
Syrene, Ambra's daughter also wanted the Runestone. Since neither had a means of traveling through time, she married Satanis and they ruled Earth together, all the while seeking a means of getting the Runestone.
At last, both found the right spell and came back to the 20th Century, where the stone was known to be. But to gain its power, the possessor had to filter it through an invulnerable body - the only kind that could hold up long enough. Because of this, they both sought out Superman and they wound up in battle over the stone. This ended when Syrene, temporarily bested, returned to send the Runestone farther back into the past.
Both mages followed it back 100 years. Just as Satanis gained the stone, Syrene summoned his namesake Satan, who dragged him down to hell. What she did not expect was that the prince of darkness would pay heed to Satanis' words. Yet this happened and they struck a bargain. Satan sent Satanis back to Earth - 14th Century Britain - and he used his powers to enslave the local people who built a device which first drew Superman from his own time, and then brought the Runestone to him.
But before he could filter the power of the stone through the Man of Steel, Syrene appeared and the two began a duel, using their powers in an effort to gain sole control of Superman. Result - the Man of Tomorrow was split into two Supermen!
Each Superman possessed half the powers of the original - and thus, only one was invulnerable. While Satanis stood dumbfounded, Syrene acted, vanishing and taking the invulnerable Superman with her. Satanis then sent the remaining Superman back to his own time, and also probed his mind for every means of time travel known to the Man of Might. Using his magic, he closed these paths to the past.
Meanwhile, Syrene had both the indestructible Superman and the Runestone, and was filtering its power through him to her. Satanis tried to stop her, but she kept him at bay with her sorcery until all was completed. As she gained the Runestone's power, Superman, drained by the ordeal, died!
Then began the battle between sorcerer and sorceress, husband and wife. Her power was now so great that Syrene would surely have killed Satanis quickly had he not merged his body with that of the dead Superman.
With these combined powers, Satanis finally overcame Syrene and he believed he had destroyed her. In fact, Superman's reawakened conscience had sent her back to her own time.
By now, the other Superman had learned of Rip Hunter, Time Master and had borrowed his time sphere. Soon he found himself battling Satanis, still merged with his other self. However, Superman's mind rebelled against Satanis, and the mage was forced to split form him. When the Supermen touched, the residue magics re-merged the Supermen into one. The Man of steel then defeated Satanis and knocked him back to his own time to confront the wrath of Syrene.