SPELL-PHANTASMAL-BARRIER

An illusionist can create an illusion to cover an area and fool the weak-minded into thinking they are trapped. With a phantasmal barrier, the very stones will appear to move at the illusionist's demand, blocking all exits. To see through the illusion, anyone passing through it must save successfully vs. Will. This illusion is persistent and self-renewing, and each time a person passes through, he must save successfully vs. Will or find himself unable to disbelieve it.

The illusion is directly tied to the level of experience of the caster. A higher level character will have an easier time disbelieving it than someone less experienced.