Quote Originally Posted by Bears With Lasers View Post
Heck--a high-CR dragon could probably even cast AMF often enough to have it up 24/7, sans permanent emanation.
Yeah, but that would mean the dragon can't use free action cheese to use his own spells and supernatural abilities. However, as Shneeky pointed out, Spellcraft is not a class skill for true dragons (except blues, which don't reach CL 12th by CR 20), so the dragon will need either 47 hit dice (not possible by CR 20) or a class level.

Of course, you still have to make sure you jump and snatch or crush the wizard, trapping them in your AMF. Otherwise, they'll still be able to pull off dirty tricks that circumvent AMF like gate cheese, or just escape.