Actually, if it's a BArred Cage version, Gaseous Form would let you out. As would Plane Shift (of course).
The reason they couldn't beat him down is because he was invisible, flying, and displaced. Also, see my earlier note about the details of the fight. If they could all see him and all get to him, and had not been scattered by the running around and fear effects, they could have beaten on him. His AC was arround 48. He was stoneskinned. Good luck beating him down.
You mean noone had an Invisibility Purge?
OR See Invisible plus Glitterdust?
Severe, gross tactical/strategic failure on the PC's part. Among the party's three primary spellcasters, shoudlhave been some way to counter invisibility for the party in general.
And one mass fly spell gets the whole party airborn, to swarm the Theurge up close (where fireballs hit the theurge TOO, if he tries for the whole party).
As for dispelling, they tried that. Being an APL 13, no one had taken greater dispelling yet. The sorcereres tried dispelling him over and over and over, but he had a lot of levels on her and she couldn't see him for the first half of the combat. AMF was out of the question as well.[/b]
So, you took a part (APL 13), up against a CR18 encounter ... and you're SURPRISED they lost, and almost suffered a TPK?
Any other ideas beside Forecage cheese and AMF that they could have done? They began to hurt him after they dispelled his shield and fly, the pelted him with magic missles while flying. Then he took out a bow and they ran.
Like I said -- glitterdust. Even if he makes the save vs the blinding ... he's been revealed to all and sundry. And any 13+ level spellcaster without at least a PERSONAL means of seeing the invisible, needs to retire RIGHT NOW.