Who's This? The invisible dude on page 11 of Who's Who vol.XI.
How you could have heard of him: While the Destroyer has appeared half a dozen times since, it's always been either in flashback to his first story (most notably in Green Lantern Annual #4), or as an often absurd (and amusing!) cameo. His only full-on (though redesigned) appearance is quite recent, in the Green Lantern Animated Series tie-in comic's second issue.
Who else? There was a time, I, Vampire would have been a prime candidate, but a New52 series changed that. I thought about Iron Wolf, but the strip is too well-considered to truly be obscure. No, my next target is someone who scored but half a page in Who's Who vol.XI.