Board Thread:Episodic and Issue Discussion/@comment-1038387-20190118171753/@comment-1038387-20190119214942

And double checked: yep, Green Lantern #10. He was Cheops, Julius Caesar and Genghis Khan, but then decided being in the limelight was too dangerous and instead became advisors of others.

Strangely, he was an advisor of William the Conqueror, who lived before Genghis Khan.