How you could have heard of him: This is one of my blind spots, but he did make a number of appearances in Geoff Johns' Justice Society of America, so it's possible you guys all know who he is. Or at least, the most modern take on him - I'm more interested in who he was when he was picked to get an entry in Who's Who. He eventually kills himself and ends up as a zombie in Blackest Night.
Example story: Green Lantern Quarterly #12 (1944)
Who else? Closing up Volume VIII, I'm sure I could have done the Galactic Golem, but I'll wait on that. Or the Gang, but do I really want to track down old Supergirl comics? No, better to skip to Volume IX as there are some very interesting, obscure entries in there.