I dont think their powers are magic based,anyway they already fought in a Silver Surfer/Superman crossover.Initially they switched places and began to torment the other Universe's hero,later they quarreled with each other and fought transforming into their respective universes heroes and villains (such as Thanos,Wolverine,Wonder Woman,Atom,etc.) While Myx progressively lost his temper Impy remained good humoured and playful,so while it was clearly a draw for me he was the moral winner.
What happened in the What If with the Infinity Gauntlet?
by my count they have fought twice, and both times they were stalemated for they realized that they had the same capabilites(duh, right) but back in the late 80's early 90's when magneto was the leader of the new mutants impossible man and Warlock fought, and they were stalemated for the same reason they transformed, they played ping pong, tennis ,and a whole bunch...anyhoo I-man ended up losing cuz he coulnt change colors where as warlock could, and if im not mistaken that was the same reason SS and superman were able to figure out that they were being set up by the two, cuz when IM turned into the super skrull his fist was green, though it still looked like the thing
Hey this was my one and only vs. topic from before and I didn't even get half the responses. In a fight, they will stalemate. Both cannot be killed by normal means, both have reality altering abilities and for the most part, aren't often very serious anyway.
Actually, Impossible Man (with Mr. Mxyztplk help) had makeup applied to emulate Thing's arm color shade just as he did when he wanted to look human during the male beauty contest between him and Warlock. Also, Superman was fooled into thinking Super Skrull was actually Mr. Mxyztplk thus giving Impossible Man the win in their bet.