Spoilers

The deep cultures

The First Affineurs were people changed by their work with the deep cultures. The seven remembered names are the Cultivator, the Miner, the Shepherd, the Walker, the Singer, the Watcher and the Soured. Stories call them siblings because they were a chosen family. They are remembered as the founding circle of the Second Age. Mahargekdar's transformation was older.

Vampires are living people changed by the red culture. The vein culture produces a slower transformation. Crystal golems are people whose change stopped partway through, while the Archlich completed the change. These accounts describe different changes to living bodies.

Corvax says he took the Rindstone because keeping it safe in Roquelle was no longer enough. He has been preparing work at the seal's far anchor. If you hear him out, he asks you to take the Rindstone with your wheel to the central crystal, then return it to Roquelle.