A Cauldron is an underground facility where machines are built. By overriding these, Aloy unlocks the ability to control new machines. In Horizon Zero Dawn there are four major Cauldron activities, plus a fifth in Horizon Zero Dawn: The Frozen Wilds.
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.
- Cauldron SIGMA : Basic puzzles and Fire Bellowback boss fight
- Cauldron RHO : Moderate puzzles and Snapmaw and Ravager boss fight
- Cauldron XI : Eclipse camp and several robots and cultists as boss fight
- Cauldron ZETA : No puzzles and Thunderjaw boss fight
- Cauldron EPSILON FW Moderate puzzles and Fireclaw boss fight.