The Nexus Stone
The Nexus Stone appeared in Blood Omen 2. It was a cyan-coloured gemstone, mounted in gold (or a gold-coloured metal). The complete artefact was roughly hand-sized.
Umah saw the Nexus Stone while she was in the Industrial Quarter, just before she was captured by the Sarafan. Kain rescued her from the Sarafan Keep, and she told both him and Vorador about the stone when they were safely back in Sanctuary.
Umah said that she had found a huge chamber inside the main factory. The chamber housed a magic portal, held open by the power of a single artefact: the Nexus Stone.
Vorador told Kain that the stone could "bend time and space to create doorways to any location within Nosgoth", but more importantly, it was able to protect its wearer from the Soul Reaver. When Kain questioned this, Vorador offered him proof: the Sarafan Lord had worn it the day he defeated Kain. Kain realized the value of the Nexus Stone. He knew that with it, he would stand a better chance when he met the Sarafan Lord in battle again. The Sarafan Lord possessed the Soul Reaver, and would no doubt use it against him. Kain ventured into the Industrial Quarter to steal the stone.[2,3,4]
Kain found the Nexus Stone, but Sebastian - one of the vampires allied with the Sarafan Lord - was waiting for him. Kain had to defeat Sebastian before he could take it. At one point, the other vampire tried to destroy the stone, but Kain prevented him. Eventually defeated, Sebastian told Kain that the Nexus Stone's portal led "to an ancient device, deep underground" that would destroy Kain and let a new reign begin in Nosgoth (the Device).[5,6]
When Sebastian was dead, Kain collected his prize. Removing the stone, however, caused the machinery around it to become unstable. This disruption spread throughout the main factory, causing explosions and its collapse. Kain was thrown from the factory roof and knocked unconscious, but luckily he was carried back to Sanctuary by a vampire belonging to the Cabal.
Kain wore the Nexus Stone as he continued on to the Canyons, the Device and the Eternal Prison. Umah joined him to pass through the Wharves, but she stole the stone from him. She intended to face the Sarafan Lord herself. Kain was shocked and angered by her betrayal. He threatened her, and Umah left. When he caught up with her again, she was mortally wounded. Rather than save her with his blood, he reclaimed the Nexus Stone and killed her for her treachery.
Kain had the Nexus Stone when he finally faced the Sarafan Lord on the metal structure above the Hylden Gate. He had learned from Janos Audron that the stone was required to close the gate once and for all. Kain managed to knock the Sarafan Lord off the platform, but the Lord quickly re-materialized behind him. He told Kain that while Kain kept the stone to preserve his life, the gate would remain open. It was a stalemate, but time was on the Sarafan Lord's side. He would eventually win if Kain did nothing.[9,10]
Kain responded by throwing the Nexus Stone into the Hylden Gate, regardless of the danger he was putting himself in. Closing the gate would kill the Hylden already in Nosgoth, and prevent more arriving. The gate sealed and collapsed, but not before the Sarafan Lord had thrown Janos Audron through it. Janos was trapped within the Demon Realm; the hated place of banishment that the Ancient Vampires had sent the Hylden to after their wars.[10,11,12]
There has been some speculation on fan forums about the Nexus Stone's origin. It has been suggested that the orb of Moebius' Staff might have been made of the same material as the Nexus Stone, or otherwise enchanted with similar magic. They both had the power to weaken or disable the Soul Reaver. However, as Kain and Umah were both able to wear the Nexus Stone without difficulty, it clearly didn't incapacitate vampires like Moebius' staff could.
- [BO2] Umah to Kain and Vorador: "I was in the heart of the main factory in the Industrial Quarter. Before the guards discovered me, I had found a huge central chamber that housed some kind of... magic portal. The portal looked into a place the likes of which I had never seen before. And this portal was held open by a single source of magic - a stone, set on a pedestal.
Vorador, I believe it was the Nexus Stone."
- [BO2] Vorador to Kain: "The Nexus Stone is an item of great power. It can bend time and space to create doorways to any location within Nosgoth."
- [BO2] Vorador: "One who wears the stone cannot be harmed by the Soul Reaver."
Kain: "And is this but a legend, to be proved false at the fatal moment?"
Vorador: "Oh no, no legend at all. It has been proven. The Sarafan Lord wore the stone when he defeated you two hundred years ago."
- [BO2] Kain to Vorador (referring to the Sarafan Lord): "He is a touch more powerful than I expected, and he has the Soul Reaver. Strange that you did not tell me this at the first."
- [BO2] Sebastian (referring to the Nexus Stone): "I will destroy this precious jewel!"
- [BO2] Sebastian: "The Nexus Stone's portal leads to an ancient device, deep underground, that will spell your destruction, Kain. A new reign will begin in Nosgoth."
- [BO2] Vorador to Kain: "You are fortunate. One of our vampires saw you thrown from the roof of the factory as it was destroyed. He carried you here. The Sarafan were too occupied to notice you."
- [BO2] Umah: "I shall be the one to find and kill the Sarafan Lord, and Nosgoth shall belong to the vampires once again."
Kain: "You fool. You have not the smallest chance of surviving such a battle.
Now, give me the Nexus Stone, or I shall pry it from your thieving fingers as you convulse in death."
- [BO2] Janos to Kain: "I can teleport you to a place near the gate, but you will have to close it on your own. Use the Nexus Stone. Cast it into the gate, and the magic of the stone will destroy it utterly."
- [BO2] The Sarafan Lord: "Do you still believe you can prevail? While you possess the Nexus Stone, my sword cannot slay you, but while you bear the stone to shield your life, you cannot use it to destroy the gate.
Stalemate, Kain, and mine is the waiting game. As long as I have not lost, in time, I am sure to win."
Kain: "But I have not yet made my choice."
- [BO2] Janos to the Sarafan Lord: "But not for you, Hylden, who has dared to set a corrupting foot upon this world after your banishment. Return to the demon dimension in which you belong."
- [BO2] The Sarafan Lord to Janos: "I sentence you to the hell of your own making - a prisoner for all time."