First appearance = Steel, The Indestructible Man #1 (March 1978)


No, he wasn't responsible for the explosion that resulted in Hank Heywood becoming Steel or anything, but a few pages into the story we get this page:


But after that: nothing, except for a headshot of Baron Death in the bottom corner of the last page of the story:


But . . . whatever became of the Baron?!?
As far as I'm aware, he never appeared in any other stories.
(Now whether that was because of Steel being cancelled after issue #5 due to the "DC Implosion" or maybe Gerry Conway just forgot about him, I have no idea.)