You solidify extraplanar shadow, creating a solid prison of darkness.

This mystery immobilizes the subject in a prison of shadowstuff. This prison blocks both line of effect and line of sight to the creature inside it, and is impenetrable from the outside. The creature inside the prison takes 1d6 points of cold damage at the beginning of each round that it remains inside the prison.

Once each round as a standard action, a creature caught in the prison can attempt a Fortitude saving throw against the spell’s original DC to break out of the prison. Success means that the creature can move out of the prison, and it fades to nothingness. Failure means that the creature takes 1d4 points of Constitution damage and remains trapped.