Precursor Ruins: Secrets
The Precursor Ruins hide a few secret room, housing some extra chests to pilfer for more precursor technology.
To reach this room, you will first need to reach the room where you fight the Heavy War Drone. In the middle of this room, there's a hidde proximity sensor that will open a door somewhere else. Just walk through the room at ground level and you should trigger it. Then backtrack a bit to reach the small hallway between the War Drone room and the molten iron room. You can dig a small path in ground there with your Manipulator (see picture below). Use your Microsphere to reach the room below where you'll find 2 Omnicannons, 1 Precursor Spider Drone and 1 Spiderwalker. Head to the right of the room (the hidden proximity sensor open the second gate) and activate the switch in this room. Climb back to the molten iron room with your Microsphere and you will find a hole in the roof of the room. Climb up there and you will find a Storage Pod inside a small room (you will need to step on the pressure plate above to open the small room).
Room near the Erchius Converter
At the bottom of the long elevator, near the room where you can find the Erchius Converter, you can use your Matter Manipulator to dig a hole in the ground and reach a room containing three extra containers.
Room in the Precursor Soldiers area
If you keep going to the left from the last room, you reach the area guarded by several Precursor Soldiers where you need to activate a console to open the small path in the elevator. That console also open a small path in the room below, which you can follow with the Microsphere and reach a room with 4 small chests.
Elevator room
You may have noticed a locked door on the left wall of the long elevator. To open this door, you will need to procede a bit further in the dungeon: use the Microsphere to enter the small passage in the elevator and follow the normal path. Opening the door leading to the room with the lava pool (in front of my character in the picture below) will open the door to the room in the elevator, so you will need to backtrack there after reaching the lava pool room. The room contains 2 small chests and a checkpoint.
In the small room preceding the lava pool room, there's a hidden trapdoor under the stairs that you can open by interacting with it. It will lead to a small room containing 3 small chests and 1 bigger chest.
Crucible room
Inside the room containing the Chiropterror right before the War Bot, use your Precursor Microsphere to climb the wall to the left. You will find a room with a Precursor Crucible. You can also see a small passage above the Crucible. Following it will lead you back in the room where you find the switch opening the room above the molten iron pool.
