Phylacteries are vials of blood taken from mages by the Templars and Chantry.

[ Iorveth explains as he walks, headed in the direction of the division leaders offices. ]

In the event that a mage goes rogue, or escapes, they're used to track them down and drag them back to their cages.

[ When Iorveth first arrived here, he'd idly wondered at what would be done if Rifters simply told the Inquisition 'no' when they were asked to help. Now he knows. ]