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"The lesson will be taught in due time, Aloy. Until then, we wait."
This article contains heavy spoilers. Read ahead with caution.

"The whole mountain -- and whatever the Old Ones built inside it -- torn out from within!"

The Mountain that Fell is the twentieth main quest in Horizon Zero Dawn.


After hearing GAIA's Dying Plea and learning the location of the weapon that will allow her to defeat HADES, Aloy makes her way to the GAIA Prime facility.

Scaling the Bitter Climb, Aloy encounters a number of hostile machines protecting the way, including a Stormbird close to the summit. Defeating the machine, Aloy continues to find the aftermath of GAIA's sacrifice; a hole blown through the mountain leaving the facility in ruins. Following the route Sylens prepared for her, Aloy meets with his hologram in his workshop above the ruins.

After he briefly explains how he came to find the ruins, Aloy voices her skepticism about repairing GAIA after witnessing the extensive damage. Sylens directs her attention to the present task: stopping HADES.

GAIA Prime

Gaining access to the first section of the facility, Aloy finds nothing more than a datapoint of an interaction between the Alphas. Finding her way outside, Aloy realizes she must cross the chasm to explore the other half of the facility.

Exploring the second half of the facility, Aloy discovers more logs of the Alphas after they were sealed into the facility. She eventually finds herself in Elisabet's room where she discovers a number of her journals. As they are severely damaged and corrupted, rendering them unreadable in their current state, Aloy scans them so that her Focus can recover the files. Continuing on, Aloy comes to a room where a holographic shrine to Elisabet has been set up. A file left from Charles Ronson explains that six hours after GAIA was deployed one of the access seals malfunctioned, leaving a gap of ten millimeters instead of the standard two millimeters. This malfunction allowed an energy signature to pass through, alerting the robot swarm of the facility's location. The only solution was to seal the hatch from the outside. While the Alphas argued amongst themselves who should go, Elisabet sacrificed herself to close the hatch. Knowing that it was too late to try and re-enter the facility, Elisabet departed for her home. This realization causes Aloy to both mourn Elisabet and marvel at her drive and conscientiousness.

Continuing to climb the facility, Aloy spots a section of the facility that appears to be intact despite the blast. Sylens informs her that this is the control room. Hoping to find the Master Override here, Aloy makes her way over, finding another datapoint of Ted Faro's increasing despair and helplessness.

Arriving at the control room, Aloy unlocks the hatch to reveal the bodies of the Alphas gathered around a conference desk. Noting that air rushed in instead of out the moment the hatch opened, Aloy begins the hologram. It begins with the Alphas unable to access the core control. Ted Faro's hologram then appears before them. He discloses his concern about gifting the future humans with their knowledge. Believing that this will only result in history repeating itself, Ted Faro reveals that he purged APOLLO and subsequently activates the ventilation of the control room, suffocating and killing the Alphas. After an interaction with Sylens, Aloy retrieves the Master Override from the desk.

Sylens' Past

Aloy returns to the workshop to find Sylens waiting for her, telling her that their journey together has come to an end. Knowing that she is deserving of an explanation, he goes on to explain that he was the one that discovered and revived HADES. Recognizing that HADES was a source of vast amounts of knowledge, Sylens agreed to carry out its wishes by forming the Eclipse cult. He mentions that HADES wasn't interested in Meridian but rather the Spire. Recalling that it was MINERVA, GAIA's code-breaking module responsible for transmitting the codes that would deactivate Faro's robots and shut down their biomatter conversion systems, Aloy realizes that HADES means to use the Spire to reawaken the Faro machines so they can destroy the world once again.

With further prompting, Sylens describes more about how he discovered HADES and subsequently formed the Eclipse in exchange for knowledge. Sylens then leaves his lance and workshop to Aloy before finally departing. After listening to some datapoints of the interactions between HADES and Sylens, Aloy fits the Master Override to Sylens' lance. Now in the possession of a weapon that will allow her to defeat HADES, Aloy journeys back to the Palace of the Sun in Meridian to warn Sun-King Avad of the coming threat to their existence.


  1. Go to the Bitter Climb
  2. Go to the Ruins of GAIA Prime
  3. Climb up the Outcrop
  4. Talk to Sylens
  5. Go to the Door
  6. Search the Ruins for the Master Override
  7. Examine the Shrine
  8. View the Hologram
  9. Talk to Sylens
  10. Search the Ruins for the Master Override
  11. Examine the Control Room
  12. View the Hologram
  13. Talk to Sylens
  14. Claim the Master Override
  15. Return to Sylens' Workshop
  16. Attach the Master Override to the Lance



The Mountain That Fell - Very Hard - No Damage - Video Guide



The following datapoints are obtained automatically during this quest and cannot be missed.

Hologram Datapoints

Text Datapoints - Quests


In addition, the following datapoints can also be found during this quest. The player can return at any time if they are missed.

Audio Datapoints


  • After Ted Faro reveals he destroyed the APOLLO archive, Samina Ebadji is noticeably moved to tears, and two other Alphas go over to comfort her.
  • The fifth Power Cell needed for the side quest Ancient Armory can be found inside the mountain to the left of the rappel point.
  • The deletion and subsequent loss of the APOLLO Archive has been foreshadowed in Deep Secrets of the Earth, should Aloy interacts with the APOLLO ARCHIVE 200 in Central Projects of Zero Dawn Project Facility, where a message shows the following: "::ARCHIVE STACK ERROR ::CODE LOCK EXCEPTION 01 ::ALL DATA LOST".
  • Playing on Story difficulty removes the major machine encounters (i.e. Stormbird) from the mission, and it's possible to avoid the others entirely by taking a circuitous route. Nonetheless, Aloy will still complain to Sylens about being forced to go through an army of machines to get to the bunker.
Horizon Zero Dawn Quests
Main Quest A Gift from the Past - Lessons of the Wild - The Point of the Spear - Mother's Heart - The Proving - The Womb of the Mountain - A Seeker at the Gates - The War-Chief's Trail - Revenge of the Nora - The City of the Sun - The Field of the Fallen - Into the Borderlands - The Sun Shall Fall - Maker's End - The Grave-Hoard - To Curse the Darkness - Deep Secrets of the Earth - The Terror of the Sun - The Heart of the Nora - The Mountain That Fell - The Looming Shadow - The Face of Extinction
Side Quests A Daughter's Vengeance - A Moment's Peace - Acquired Taste - Ancient Armory - Blood on Stone - Cause for Concern - Farewell - Death from the Skies - Fatal Inheritance - Heap of Trouble - Honor The Fallen - Hunters' Blind - In Her Mother's Footsteps - Insult to Injury - Queen's Gambit - Redmaw - Robbing the Rich - Sun and Shadow - Sunstone Rock - The Forgotten - Traitor's Bounty - Underequipped - Weapons of the Lodge
Errands A Curious Proposal - Collateral - Deadliest Game - Demand and Supply - Hammer and Steel - Healer's Oath - Hunting for the Lodge - In Foreign Lands - Luck of the Hunt - Odd Grata - Sanctuary - Shortage of Supplies - Sun's Judgment - To Old Acquaintance
Activities Bandit Camps Blackwing Snag - Devil's Thirst - Gatelands - Hollow Fort - Shattered Kiln - Two-Teeth
Cauldrons Cauldron RHO - Cauldron SIGMA - Cauldron XI - Cauldron ZETA
Corrupted Zones Corrupted Zones
Hunting Grounds Greatrun - Nora - Spurflints - Sun Furrows - Valleymeet
Tallnecks Copper Deeps - Devil's Thirst - Rustwash - Spearshafts - Sun-Steps
Horizon Zero Dawn: The Frozen Wilds Quests
Side Quests Firebreak - For the Werak - Frontier Justice - Into the Frozen Wilds - The Forge of Winter - The Hunters Three - The Shaman's Path - The Survivor - Waterlogged
Errands A Secret Shared - Ikrie's Challenge - Geared Up: Forgefire - Geared Up: Icerail - Geared Up: Stormslinger - Out of the Forge - The Claws Beneath
Activities Tallneck: Frostfigures - Snowchants Hunting Grounds - Stone Yield Bandit Camp