About 1,100 m east of the Lifepod (the map marker is granted after the Tadpole Pens objective), the Alien Ruins is a deep, murky zone of alien buildings, outposts, towers, a power plant and a viral/infected sector. It is the core mid-game story system.
The questline: use a Sonic/Feedback Resonator to destroy three bloom cankers (in a ravine, the Metal Farms, and the Cicada Wreck) to earn the Axum Vision Adaptation (read alien text); gather repair ingots (10 Titanium, 10 Strontium, 10 Mangalloy) to fix the turbine; then operate observatory levers and holograms. Rewards include an Engine Efficiency Upgrade and a hologram revealing the future Xanadu region.
The Collector Leviathan patrols the deep approach — swim near the surface to avoid it, distract Needlers with flares, and stage a forward base with respawn capability before committing.