The Seer´s Cage

This Seer's Cage was an indestructible metal cage forged by the Seer. It was designed so no magic could ever leave the cage, though magic could enter it. The cage was made to imprison even the most powerful magical beings. Prue Halliwell was once entrapped in the cage.

History
Centuries ago, the Source of All Evil felt threatened by a demon known as the Tall Man but was unable to vanquish him. In order to secure his position as leader of the Underworld, he ordered the Seer to forge a cage powerful enough to hold the Tall Man for all eternity.

The Seer freed the Tall Man after the Source was vanquished in order to obtain Phoebe Halliwell's unborn child. The Tall man was meant to teleport Phoebe into the cage but instead trapped Paige Matthews. When her unborn child took control of Phoebe, it teleported her to the Underworld, where the Seer took the child from her and locked her in the cage as well.

As the Seer prepared her coronation, Phoebe and Paige summoned Piper to the cage. When the Seer tried to kill them with the child's power, the Charmed Ones protected themselves with the Power of Three spell. The Seer was then overwhelmed by the child's power and vanquished herself and all demons present. The resulting explosion also rendered the cage powerless and easily opened with a kick.