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 Material 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 Blue Heart - as well as revealing a mural depicting the blue altar[SR2][SR2-C6].
The Blue Heart constantly dripped bright blue glowing blood and once gained the heart significantly limited Raziel's abilities - preventing him from Climbing, Gliding, entering Combat, manipulating objects or Devouring Souls.[SR2].
Returning to the bottom of the forge and the blue altar, Raziel restored the Blue Heart to the blue mummy, activating the altar room. This caused the blue 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.[SR2][SR2-C6]
- The Blue Heart is not named in game, but it is referred to as such in the Prima Guide. Within game files, it is referred to as "arkey_c".[SR2]
- 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.[SR2-C6]
- The puzzle of the Air Forge and colored hearts notably foreshadows the events surrounding the death of Janos Audron[SR2][SR2-C8][SR2-C9].
- 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 Blue Heart representing Spectral entities and the Spectral Realm.
- Similar to Moebius's Staff, the large snake sculpture in the Air Forge disabled the hearts of Vampires, enabling them to be extracted.
- The Blue heart and its puzzle are featured extensively in early video trailers of Soul Reaver 2 and the Air Forge demo, both of which showcase different stages in the development of the puzzle. Notable differences include different enemies in different positions, different particle effects, different combat moves, different HUD icons, a different heart mural, a different Light crystal to obtain the heart and even a 'solution mural' positioned on the floor of the chamber.[SR2]