At the bottom of the main chamber of the Air Forge, Raziel found three colored sacrificial altars with mummified victims missing their hearts and bound before a giant stone head. Following the Dark path, Raziel was able to make his way to a high darkened chamber and activate a Light crystal with the Light Reaver, illuminating the room and dispensing the Red Heart - as well as revealing a mural depicting the red altar[Soul Reaver 2][Soul Reaver 2/6][Soul Reaver 2 strategy guide (Prima)].
The Red Heart constantly dripped bright red glowing blood and once gained the heart significantly limited Raziel's abilities - preventing him from Climbing, Gliding, entering Combat, manipulating objects or Devouring Souls.
Returning to the bottom of the forge and the red altar, Raziel restored the Red Heart to the red mummy, activating the altar room. This caused the red mummy and heart to heal and disappear, spawning a single soul and animating the large head, which quickly devoured the soul of the mummy and exhaled an updraft which Raziel could use to guide further up the forge.[Soul Reaver 2][Soul Reaver 2/6][Soul Reaver 2 strategy guide (Prima)]
- The Red Heart is not named in game, but it is referred to as such in the Prima Guide.[Soul Reaver 2 strategy guide (Prima)] Within game files, it is referred to as "arkey_a".[Soul Reaver 2]
- When held by Raziel, each of the colored hearts can be heard beating loudly. If the hearts were placed into the mummy at the wrong altar, the stone head would become animate and Raziel would be shot by a beam from the crystal on its head, sending him into the Spectral Realm in the same manner as Sentry eyes - in this case the heart would not disappear and would remain stuck in the ribcage of the unrestored mummy.[Soul Reaver 2/6]
- The puzzle of the Air Forge and colored hearts notably foreshadows the events surrounding the death of Janos Audron[Soul Reaver 2][Soul Reaver 2/8][Soul Reaver 2/9].
- The Air Forge was conceived as a place where the Ancient vampires sacrificed their enemies (and later the vampires themselves) by feeding their souls to the Elder God, with the heads representing the Elder and the Red Heart representing flesh and the Material Realm.
- Similar to Moebius's Staff, the large snake sculpture in the Air Forge disabled the hearts of Vampires, enabling them to be extracted.
- SR2 Air Forge and Defiance Forges at DCabDesign (by The Hylden), post #3 (by Daniel Cabuco)