Mass

Blood Omen 2 era
In Blood Omen 2, the Mass was the ancient and "eternal" creature that lived inside the Device. It was deadly - "capable of killing any living thing with but a thought", yet "harmless without a channel for its mind". The Device was useless without the Mass and it may have been unique as the Builder claimed it was his creation. It looked more like a plant than an animal - like a giant jellyfish.

During the war with the Ancient Vampires, the Hylden built the Device to house the Mass, and attune its mind to kill their enemies. They wanted to purge Nosgoth of all creatures except their race. However, the Device's network - required to direct the Mass' lethal mental energy onto Nosgoth - was never completed. The Hylden were banished to the Demon dimension before they could finish it.

The Device and the Mass lay dormant beneath Meridian until the Sarafan Lord re-entered Nosgoth (through the chain of events shown in Defiance). He brought others of his race through the Hylden Gate with him, and they started to work on it again. Janos Audron was imprisoned within the Device, and his blood was used to feed the Mass. Its parasitic demands caused him to devolve into the Beast.

When Kain learned of the Device from Sebastian, he knew he had to destroy it before the Sarafan Lord could use it. He found the Builder - the architect of the Device - in the Eternal Prison. Kain realized that the Glyph energy pipes, installed all around Meridian, were the conduit the Sarafan Lord had built to conduct the Mass' mental energy. The Builder did not want to see the Device used anymore, despite it being his creation. He told Kain to kill the Mass, "that which [he] created out of arrogance and pride".

The Builder offered his blood to Kain. He said the Mass could not withstand "pure blood from the elder races" (see the encyclopaedia entries for the Beast and the Builder for more about this). Kain drank, and returned to the Device with the Builder's blood in his veins. He used it to poison the creature. Kain slit his own wrist, and allowed a relatively small amount of blood to fall into a tube-like appendage of the Mass (probably its feeding tube). The effect was instant - the Mass immediately began to rupture and haemorrhage. As it died, Janos was able to regain some of his strength and return to his normal winged form.