See also Quellers.
Once locked around a subject's neck and activated, mages lose their ability to work magick, werecreatures are unable to change form or use Gifts, and both ghouls and vampires are severely (but not entirely) weakened in their supernatural abilities.
Control collars also strip K'Nes mages of their magickal abilities. When used on a Jurvain, they cut them off from the Commonality hive mind, as that is itself a magickal effect (the drug Somjijok has a similar, albeit temporary, effect). Control collars have no effect on Horadrim Soul Web nanobots or their related abilities, as those are almost purely technological. It is not know what effect control collars have on Vulthra (as it has never been sucessfully tried).
More advanced models also contain transponders so wardens can keep track of their prisoners' movements. Some also contain remote-controlled explosives to detonate and kill prisoners if necessary, or electro-shock devices to immobilize escaping prisoners in a (usually) non-lethal manner.
In pre-Imperial times, control collars were primarily used by the Raptors and Crusader Teams to secure supernatural prisoners, although they were also occasionally used among the Light Infantry in maximum security prisons containing awakened prisoners. Their Imperial successors use them in similar roles, although they are also used as a temporary security measure by many among the upper nobility when allowing awakened commoners into their august presences.
K'Nes have their own form of control collars, presumably to keep their own aberrant mages in line. They also work on human prisoners, however, as demonstrated when Praetor Narrah used one to secure Alistar Dimiye after the Second Battle of Midgar during the Third Civil War.
Behind the ScenesEdit
Introduced to the TI universe in season 4.3, control collars were essentially MacGuffins to strip player characters of their supernatural abilities when their plotlines required it. Many details such as how they work, cost, availablily, legality, limits and weaknesses have not yet been established and are open to development or revision.