Slave bracelets can constrict and induce a choking sensation in the slave when the master wishes them to. Some bracelets may also cloud the victim's memory for a substantial period of time after they are first attached, although they are not always 100% effective. Memory-clouding slave bracelets are the most expensive kind, but also the most desirable.
Slave bracelets only "answer" to one master. If someone is foolish enough to slip on a slave bracelet of their own free will, the first shadowling to assert dominance over that person will become the master. Old folk tales tell of unwary travelers tricked by shadowlings into donning their bracelets, only to end up being sold into slavery.
If a slave bracelet is used pursuant to a bargain, the bracelet will release itself automatically at the conclusion of the bargain. However, slave bracelets rely on the minds of their hosts to monitor completion, which means that slaves who suffer from memory loss may end up being enslaved long past the term they agreed to serve for.