Originally Posted by Sunken Valley
That stuff cannot be penetrated by a high CL. how did Xykon break out. I find your information makes it hard to believe he meteor swarmed out and he wasn't epic back then
I always got the impression that he was epic, he just didn't really do much with it. Then he bacame undead, got an int boost, and lost his only real passion in life.
As for getting out of the cave, Superb Dispelling (mentioned by fitsclowningham above) could have don it. Its the dispel he used against Evil V, and its not in the PHB or even Spell compendium, making me think it is an epic spell that Xykon created for himself. Unless it comes from some other source...