King Tut
Mark why don't you Phantasmal Force someone healing the Prince, and then him getting up and freeing himself? I think that would cause a lot more confusion than just some flames.
I forget how long Hold Person lasts, but it's just you 2 vs. 3 priests...I think you might look for something to turn the tide more than just flames (plain physical damage might not really spook these guys, but the Prince getting away, or something like that, might).