Who's This? The black-clad mystery man in Who's Who Update '87 #4, page 27.
How you could have heard of him: As the Phantom of the Fair, his connection to Sandman would be reused in an eponymous story arc in Sandman Mystery Theater (#41-44, 1996). When Malibu Comics started using old Centaur characters as their Protectors, the Phantom was re-imagined as Gravestone, not that anyone us supposed to remember any of that more clearly.
Example story: Amazing Mystery Funnies vol.2 #7 (#11 overall, 1939) by Paul Gustavson
So though other heroes patrol entire cities, or even planets, the Fantom only looks after a single theme park. How much crime can there be at New York's World Fair? Enough for 14 stories? Well, in the first installment, a sniper shoots the rope holding a painter's scaffolding and he would have plummeted to his death had the Fantom not swung in to save him. The next swing takes him to the sniper's rooftop where...
Meanwhile, the authorities are looking up the Fantom in a book of Scandinavian legends, as they relate to the Fair... uhm... I don't know what's going on there.
No matter, when we catch up with the Fantom again, he's breaking desks (see the cover, above) and giving Occo a good talking-to. But the mall cop shows up, so the Fantom escapes, the art absolutely refusing to follow the narration's order to draw a proper chandelier.
Who's Next? A character who really only exists because of a licensing problem.