The ter'angreal is a black stone ring.
With a touch of the user's blood, the ter'angreal grants the wearer incredible strength and speed, as well as the ability to shroud themselves in shadows. The ring drastically shortens a person's lifespan, however, but as Bloodknives are used for suicidal destructive missions, they are the only ones who wear the rings, as they expect to die shortly anyway. Removing the ring can slow the dying process slightly. Demandred mistook the effect, including the lethality to the subject, for "Nights Shade", a weave from the Age of Legends, hinting at a connection between the two.