I saved after entering Cet's domain. Now, of course, the door is locked. Will Cet ever change to a different form? If I approach, he kills all of my group. If I run to the closed door, he apparently can't come up the small tunnel, but now what? My Vanish spell just teleports me back into the room, and all my other spells, call home etc don't work? Is there anything I can do????

Are you suggesting you are in there WITHOUT the black fire charged mavin and staff??? What's wrong with the "slowly hack the ugly bugger to death" philosophy? No, I don't think there is any postponing the inevitable, I don't think you have any way out of the chamber. You should only be in there if you are ready for the big battle. If you desperately want out, then it is reload time methinks.

PS, the only time Cet changes form is if you accept the option for your speaker to be taken over by Cet - this peeves off Anephas no end.