Project Zero Dawn envisioned a series of underground facilities to rebuild a lifeless Earth. These facilities would be controlled by GAIA while the subfunction HEPHAESTUS would oversee construction of Cauldrons where specialized robots would be designed and constructed for use in terraforming.
There are five cauldrons in the world of Horizon Zero Dawn, four of which are accessible.
- Cauldron PSI: Corruptor boss fight to unlock PSI overrides
- Cauldron SIGMA : Basic puzzles and Fire Bellowback boss fight
- Cauldron RHO : Moderate puzzles and Snapmaw and Ravager boss fight
- Cauldron XI : Eclipse tribe camp and several robots and cultists as boss fight
- Cauldron ZETA : No puzzles and Thunderjaw boss fight
Every cauldron unlocks its own overrides and by completing a cauldron, the player unlocks the ability to override a few new machines.
Main Article: The Womb of the Mountain