Three of my all-time favorite covers from DC are the three Showcase comics covers by Joe Kubert featuring Nightmaster. Aside from these tasty images, Kubert had nothing else to do with the character who is sometimes mentioned as the first sword and sorcery character in comics (not true). The story written by Denny O'Neil. in the debut issue was drawn by the painfully overlooked Jerry Grandenetti and the last two issues of the singular trilogy are famously drawn by an up and coming Berni Wrightson, still a raw talent learning his craft on the job before our very eyes. You can read all three Nightmaster Showcase adventures here, here, and here.
Here's Nightmaster as rendered by Wrightson for a fanzine. The promised series featuring the character did not materialize. In fact after this three-part story, the character vanished for many years until surfacing in the pages of Animal Man and later Swamp Thing. Eventually he became part of DC's magical team Shadowpact and even rated a one-shot comic of his own which sported a new Wrightson cover.
But for the most part, Nightmaster is what he always was, a weird blend of superhero and sword and sorcery, a could'a been comic book character. But those are still some blockbuster Kubert covers.