Mass

"The foul Mass, hidden within the bowels of the Device. Here was the Sarafan Lord’s ultimate weapon – his trump card, to be played against human and vampire alike. But I had my own weapon. I could feel the Builder’s blood course coldly through my veins. If I could use it to poison this creature, the Sarafan Lord’s plans would be ruined."

- Kain

The Mass was an ancient, powerful and presumably unique life-form that was featured in Blood Omen 2. It was originally used by Ancient Hylden in the Vampire-Hylden war who intended to use its mental powers to attack their enemies as part of The Device. The Device was incomplete at the time of the Hylden banishment, though the immortal Mass survived inside the Device for centuries, eventually being uncovered by the Hylden Lord in the Post-Blood Omen era. In his guise as the 'Sarafan Lord', the Hylden general gained control of Nosgoth and ordered a Glyph magic network be constructed to complete the Device. When Kain returned, the Glyph magic network was virtually complete and on the advice of the Builder of the Device, Kain killed the Mass to prevent the Device being used.

Role
The Mass was an 'eternal' creature that, although naturally 'harmless' had potent mental powers and was able to kill with its thoughts. At some point in the Vampire-Hylden war era, the Mass was presumably captured or created by the Ancient Hylden who intended to use its mental energy as a weapon against their enemies. To this end, the Hylden (specifically the Builder) designed and constructed the Device to house the Mass and attune its mind to eliminate all life-forms not of the Hylden race. However, for the Device to be effective it required a conduit to project the thoughts of the Mass onto and before it was completed, the Builder was imprisoned in the Eternal Prison and the Pillars were raised, banishing the Hylden to the Demon Realm.

For Centuries, the immortal Mass and the Device housing it remained hidden underground beneath Meridian until the Hylden attempt to re-enter Nosgoth's Material Realm reached a head in the Blood Omen era, with the Hylden Lord's possession of Janos Audron. In the Post-Blood Omen era, after using Janos to open the Hylden Gate the Hylden Lord returned his natural body to the Material Realm. Taking on the guise of the Sarafan Lord and founding the Sarafan order, he defeated the young Kain's growing empire and manipulated the Humans to take over Nosgoth. During this time, The Device was secretly uncovered and Janos imprisoned within to feed the Mass, as the Hylden - disguised as Glyphwrights - completed and maintained a glyph magic network that would provide heat, light and to a certain degree protection from vampires (in a similar manner to electricity) to the human population. This network however could also be used as a conduit for the Device. With his blood used to feed the Mass Janos devolved into a Beast form.

When Kain returned he learned of the Device from Sebastian and was transported to the Device by the Seer. Inside Kain found 'the Beast', who told him that the Device was too great for him to destroy alone and advised him to seek the Builder in the Eternal Prison. Kain discovered the Builder and when informed that Kain was seeking to destroy the Device, the Builder was eager to help. The Builder explained the hisory of the Device and the role of the Mass and the uncompleted conduit network in the functioning of the Device, prompting Kain to realize that the Sarafan Lord (or more specifically, the Glyphwrights) had completed the network in the guise of providing Glyph magic to Meridian's (and Nosgoth's) population. The Builder informed Kain his only hope now was to destroy the Mass itself and revealed that the creature suffered from a simple weakness; the blood of the Elder Races was poisonous to it and would kill the creature. Granting the Builder the 'release' he desired, Kain killed the Builder and drank his blood.

When Kain returned to the Device in Chapter 9, 'The Beast' noted the change in him, sensing the Builder's blood in his veins and told him to use it to kill the Mass but also warned him of the Hylden he would face and how they pulled the strings of the Sarafan Order. Kain descended into the Device, eventually reaching the Mass's Chamber at the core of the device and using a series of elevators he was able to reach a 'feeding' platform above the Mass. Slitting his own wrist, Kain let a few drops of the Builder's blood drip into the 'feeding tube' poisoning the Mass, which quickly shriveled and ruptured as the creature died. With the death of the Mass, the Device was rendered useless and with Janos was no longer drained to feed it he was able to return to his usual form and escape with Kain to Sanctuary.