As well as being a pretty awesome battle, Dr. Impossible's encounter with Mr. Mystic is hilariously chaotic with plenty of teleporting, illusions and repartee which just trails off. And after all that it doesn't even have a very satisfying conclusion, leaving Impossible back where they started feeling rather bemused.
It's almost as if Dr. Impossible is that month's adversary in Mystery of Mr. Mystic, and the writers were going to have him defeated but got told at the last minute that Dr. Impossible is also appearing in that month's issue of The NEW Champions, so their hands were tied.