Part of the series:

No Man's Sky Tips & Tricks: Hub for multiplayer, QoL, rewards, and hidden questlines.

How to Use Portals & Glyphs: Required for the final quest step.

Quick Answer

The Autophage questline begins with the mission They Who Returned, added in the Echoes update.
Requirements: complete The Purge storyline and use an Echo Locator to open a Harmonic Camp seal.
The quest rewards the Scan Harmoniser, Polyphonic Core, and Voltaic Staff blueprints.
You must complete two parallel sub-missions: Prayers of the Machine and Audience with the Autophage.
The final step uses a Portal to reach a hidden Atlas Station.

Overview

The Autophage are a robotic species hidden across Dissonant systems. Uncovering them leads to unique multi-tool technology and a deeper look at No Man's Sky lore. The questline is gated behind main story progress and a Dissonant system encounter, making it a natural next step after completing the Artemis Path.

Requirements

To start They Who Returned, you need:

Complete The Purge: the final mission of the Artemis Path. If you have New Beginnings in your mission log, you have done this.
Open a Harmonic Camp seal: use an Echo Locator to find a Harmonic Camp on a Dissonant planet and solve the terminal puzzle. This also unlocks the Aeron Turbojet jetpack appearance.

Triggering the Mission

After meeting both requirements:

Travel to a Dissonant system.
Land on a planet with Dissonance Detected.
Fight Dissonance Resonators until one drops an Echo Locator.
Use the Echo Locator to find a Harmonic Camp.
At the Harmonic Interface terminal, select "Scan memory registers" to receive three simple math equations.
Input the runes matching the answers into "Input override glyphs" in any order.
Warp to a new system in your starship. A starship alert should trigger the mission automatically.

If a freighter battle occurs on the warp, warp again to receive the mission.

Meet the Autophage

A starship alert will ask you to analyze Block0, Block1, and Block2. Select Block2, which contains the odd non-alphanumeric character. Continue through the conversation until a mechanical voice reveals an attempted hijack. You will receive a waypoint to a damaged Autophage in a Harmonic Camp.

Speak with the Autophage. When prompted, offer Atlantideum to progress. Other resources do not work.

Korvax Monolith

The mission directs you to a nearby Korvax Monolith. Interact with the Discordant Interface and offer Atlantideum again. Then read all three lore options at the main pedestal to learn the Autophage number words. Return to the original Harmonic Camp.

Note: After this step, Korvax Monoliths can reward you with an Atlantid Multi-Tool.

Unlock Translation

Return to the damaged Autophage head. Its dialogue will include three numbers. Touch the head and input the matching runes. This unlocks translation and grants you the Scan Harmoniser blueprint.

Install the Scan Harmoniser on your Multi-Tool. Use it to decloak nearby Autophage in the camp. Speak with each one, then travel to the Nexus to report to Nada.

Parallel Sub-Missions

Nada sends you to speak with an Assembled Construct. Show it Atlantideum to receive the Polyphonic Core blueprint. Nada then gives you two parallel missions that must both be completed.

Prayers of the Machine

Present Atlantideum to four computerized systems:

Terminal Prime in the Nexus
A planetary manufacturing facility computer
The Station Core of the system's space station
Your personal starship's computer

Each reveals a binary phrase. After the starship step, pulse drive until a special Space Encounter triggers with a fragment of New Atlantid.

Audience with the Autophage

Install the Polyphonic Core. Visit three different systems and use the core to locate Autophage camps. At each camp, decloak and speak with the marked Autophage. Complete the task each gives you to receive a Voltaic Staff component blueprint. Construct each component in your inventory. Once all three are built, assemble the Voltaic Staff at any Autophage Synthesis Terminal.

Reach the Hidden Galaxy

Use your scanner to find a Portal. Present Atlantideum, display your Voltaic Staff, and say "Atlas", in any order, to activate the Portal. You will briefly be teleported into space, then to an Atlas Station.

Your Life Support will drain during the space sequence, so top it up beforehand. At the Atlas Station, present Atlantideum to trigger a final dialogue and corruption sequence.

Completion

Leave the Atlas Station and report back to Nada on the Nexus. You receive:

Scan Harmoniser blueprint
Polyphonic Core blueprint
Three Voltaic Staff component blueprints
A new guide entry about the Autophage
The ability to encounter Autophage camps and settlements naturally

Afterward, the next pulse drive will trigger the follow-up mission, In Stellar Multitudes.

FAQ

Do I need a settlement before starting this quest?

No. The Settlers mission and owning a settlement are not required.

Do I need to fly a Sentinel ship to trigger the mission?

No. You do not need to retrieve a Sentinel Interceptor or fly one. The Harmonic Camp seal is the key requirement.

Can the mission trigger in a freighter warp?

No. Warp in your personal starship. If a freighter battle interrupts, warp again.

What is Atlantideum?

Atlantideum is a resource found in Dissonant systems and Harmonic Camps. It is used throughout the Autophage questline as an offering.

Is the Voltaic Staff always S-class?

No. The assembled Voltaic Staff has a random class, and some slots may be damaged.

Key Takeaways

Do the prep in order: finish The Purge, then farm Dissonance Resonators until one drops an Echo Locator, then solve the Harmonic Camp terminal. Nothing triggers until that seal is open.
Stockpile Atlantideum before you begin. It is the offering at nearly every step, from the damaged Autophage to the Korvax Monolith to the Portal and the Atlas Station, and no other resource substitutes.
Warp in your personal starship to trigger the mission. A freighter warp will not do it, and if a freighter battle interrupts the jump, simply warp again.
Top up Life Support before you activate the Portal. It drains during the brief space sequence, which is the easiest place to lose progress.
Run Prayers of the Machine and Audience with the Autophage side by side rather than one after the other. Nada will not move you on until both are finished.
Do not count on a good staff. The assembled Voltaic Staff rolls a random class and may have damaged slots. Once you report back, your next pulse drive starts In Stellar Multitudes.

No Man's Sky Autophage & They Who Returned Questline Guide