The Carstein Ring was the fabled ring of Vlad von Carstein himself.
If a Vampire of the Von Carstein bloodline were to wear this ring, they become magically armoured and able to quickly regenerate wounds dealt unto them. If the wearer is killed, he returns to un-life at dusk, completely healed. Legend has it the Carstein Ring was created by Nagash himself as a gift for Vashanesh. Through the ring, Nagash was able to control the Vampires and make them his warrior-slaves. To free the Vampires from this control, Vashanesh killed himself, knowing that the ring would eventually return him to un-life and that, without the Vampires, Nagash would fall.[1a]
The Carstein Ring was most famously worn by Vlad von Carstein during the Wars of the Vampire Counts, during which it saved him from final death many times. It was stolen from him by an Imperial thief, though rumour has it the thief would not have been able to approach Vlad if it wasn’t for the treachery of Mannfred von Carstein who magically aided him, shielding the thief from Vlad’s gaze. It has not been seen since.[1a]