illusion mental visual 

Traditions arcane, occult, primal

Cast [>>>] somatic, verbal

Range 120 feet; Area 20-foot burst

Duration 1 minute

You shroud an area in illusory dreamstuff, making the ground look and feel like a deep mire or quicksand. Ground in the area is difficult terrain.

Each creature in the area when the spell is cast, or that enters the area, must attempt a Will save. On a failure, it believes it's being pulled down by the earth, taking a –10-foot circumstance penalty to its Speeds. On a critical failure, it's also immobilized. In addition to the normal actions to Escape, at the end of an affected creature's turn, it can attempt a Will save, removing the effects on a success. On a critical success at any Will save made against oneiric mire, the creature fully disbelieves the illusion and no longer needs to make Will saves to risk a Speed penalty or being immobilized, though the area is still difficult terrain.

Secrets of Magic, page 119.