not sure
Well, this is some of the story elements that don't make sense, and seem to render the "prophecy" pretty stale and useless. That's why TDC is a "one" movie. . .movie. Anything following it up, bringing back Skesis and Mystics doesn't add up to much, and creates a huge amount of story problems and continuity. A lot of it comes from the novel itself (which is a great read, and adds more insight) and Augrhas tale found in the Brian Froud book, which outlines just about everything in the world of Thra.
I would love to see more Skesis, they stole the film if you ask me, wonderfully designed, but on a level of storytelling, it doesn't make any sense that they return. It waters down the purpose of the prophecy, Jen's quest, and the healing of the crystal, something that was not definitive, and absolute because, i guess in this case, it happens all over again. so why did Gelflings die? why did they create the prophecy to finally heal their world, to watch it happen all over again? and the UrSkeks "left" the world, after realizing their mistakes.. . so why would they do it (enter the crystal) again. . . . .??
ahh, we could go on forever, it is strange, and doesn't quite add up yet, but once again, we will have to wait for more info.