Spirit Forge (Defiance)

Following Ariel's description, each of the elemental forges were designed as baptisms for the the Soul Reaver, and the Spirit Forge was the final one of them.

The Soul Reaver, being the spirit of Raziel, was a devourer of souls. Those souls which were devoured were simultaneously fed to the Elder God who recycled them in the Wheel of Fate, where they would be reborn in its endless cycle of birth, death and rebirth.

In Soul Reaver 1 Raziel found different elemental forges with which he could temporarily imbue the reaver with elemental attributes aligned to each Pillar of Nosgoth. By the time of Defiance the soul reaver had evolved to the point where onced imbued it retained the elemental baptism permenently. Except for the light and dark fonts, the air, water, fire, earth fonts had their energies guarded by the spirits of the first vampire guardians. And by using the soul reaver to devour their spirits and recycle them into the Wheel of Fate, Raziel was able to reclaim those elemental energies and acquire all 6 elemental reavers.

The Balance guardians are unique, as unlike the other guardians who are bound to the pillars using some physical token, such as Moebius' hour glass or Mortanius' death orb; they are bound by their very souls. Kain being a unique balance guardian vampire, is even able to make vampires in his own unique way, as unlike the traditional blood gift, he creates vampires by dispersing his own soul into those whom he wishes to raise, as he did with his 6 lieutenants. The soul he disperses then overtime regrows in him.

Seeing as how the balance guardians are unique, it comes as no surprise then that so is the Spirit Forge. It was the only forge attuned specifically to the balance pillar and required all 8 reavers forms to activite. Unlike the other forges, the energies of this forge were dispersed into the spirits of every balance guardian that came before Kain. When the Spirit Forge was activited it summoned each of the balance guardians and by devouring their spirits and recycling them into the Wheel of Fate, they were able to find absolution, while the energies of the Forge gave the reaver its final form, the Spirit Reaver.