Horizon Zero Dawn Explained: What Does The Ending Really Mean?

6. And Why Did HADES Activate?

This is one of the biggest questions left behind for a future game, though there are some interesting threads to pull at.

First up there's Sylens, a helper-character who formed the cult group, Eclipse, to worship HADES - who he found derelict following GAIA's self-destruct, that rendered HADES unusable.

Part of the ending shows Sylens has constructed a 'cage' to keep the floating HADES A.I. 'core' inside (though don't ask me how a computer A.I. can fly), and even he asks HADES what caused it to activate and fight GAIA in the first place.

Clearly, being HADES itself refers to the signal as his 'Master', there's a larger network of influencers at play.

The timeline establishes: 'Rogue signal activated HADES during GAIA's repopulation efforts, GAIA deactivated and destroyed HADES, Sylens finds the HADES core and reactivates him', but in showing just how easy it was for a human to access and learn from the machine archives, converse with them and create the wireless 'Focus network' of communication (all Sylens doing), it's entirely possible there's another sect of humans who discovered the machines years/decades before the events of Horizon Zero Dawn, eventually activating HADES, perhaps by accident.

Remember in LOST, how Locke thought the hatch's beam of light was 'a sign', yet it was just Desmond shining a torch? Such a comment on belief would fit very well with Horizon's comments on religion (which I'll get to).

For now, Sylens clearly wasn't the one who triggered HADES' initial awakening, but the game does end with him appearing to load HADES' A.I. into a 'FAS-BOR7 Horus' unit; the massive spider-esque machines that are used to terraform the Earth, and remain deactivated across the land... for now.