- Lost River Subnautica Guide: Not All who Wander are Dead - February 5, 2023
- The Forest Crossbow Guide: A Bow, but Better - February 2, 2023
- The Forest Sinkhole Guide – Surviving the Sinkhole - January 27, 2023
- Gel Sacks
- Acid Mushroom
- Deep Shroom
- Table Coral
- Ghost Leviathans (Juvenile)
- River Prowlers
- Blood Crawlers
- Brine Pools
Points of Interest
- Ghost Forest
- Disease Research Facility
- Lost River Lab
- Lost River Gate
- Entrances to Inactive Lava Zone and Magma Zone
Planet 4546B has no shortage of fascinating, beautiful, and terrifying biomes. The Lost River biome is all of those things at the same time. Located between the Grand Reef and the Magma Zone biomes, the Lost River is one of the most heavily populated biomes in the game, flush with veins of valuable resources and abundant sources of energy and heat.
Of course, that also means it is one of the most dangerous. This Lost River Subnautica guide will give you the rundown of what the lost river has to offer, instructions on how to get there, a list of all the different ways it can kill you, a quick overview of the points of interest within the zone, and a few pointers on how to keep yourself from ending up in the stomach of a baby ghost leviathan.
Before You Go
This isn’t the first place you visit when you get dropped into Subnautica’s ocean. The lost river is a mid to late-game location that will kill you if you aren’t prepared for it, so let’s use some of those resources you’ve been hoarding and make sure you can stay alive down there.
The most important equipment to bring into the lost river with you is a proper vehicle. The honest truth is that you probably won’t even reach the river without a pressure-resistant vehicle.
If you are visiting the lost river on a shorter excursion, or have a base nearby, then just the Seamoth or Prawn Suit should suffice. However, it is probably a better idea to bring the Cyclops down too, so you have a place to recharge your suit and store the resources you gather.
The cavernous biome of the lost river ranges in depth from just under 500 meters to around 1100 meters. With this in mind, make sure whatever vehicles you bring down with you are upgraded to withstand the pressure at these depths. Due to its increased pressure resistance and general utility, I recommend the Prawn Suit rather than the Seamoth.
Upgrading your vehicles with defensive equipment such as decoy launchers and reinforced hulls is also a good idea, as you will encounter a lot of hostile fauna. If you mean to take advantage of the large resource nodes here, you will also need the drill arm attachment for your Prawn Suit. I also typically deploy with the grapple arm to allow for better traversal.
You will need an air tank with a capacity of at least 150 and either a set of upgraded fins or the Seaglide. While this may not seem important while you’re inside the safety of your prawn suit, there are some situations where you will have to swim.
If possible, I recommend bringing either the reinforced dive suit (if you have a way to manufacture food and water nearby) or the Stillsuit (if you do not).
The repair tool is non-negotiable. If your Prawn Suit gets busted at 1000 meters down in an underwater cave and you have no way to fix it, there is no chance you will make it to the surface.
You may also want a few beacons to mark important locations and the Pathfinder tool for exploring caves. Lastly, bring lots of medkits and a Stasis Rifle unless you are confident in your ability to out-swim a leviathan.
There are four paths that will take you into the Lost River biome, each entering from a different location and carrying its own hazards.
Bulb Zone Trench
The path will take you in through the Bulb Zone biome and deposit you right at the Disease Research Facility.
bulb zone trench
Right at the border between the Bulb Zone and the Mountain Corridor, follow the foot of the mountain until you find a cleft in the seafloor at the base of a sheer drop. Look for a spiky rock formation at the top of the mountain if you’re having trouble finding it.
Follow the trail of pyro-coral down into the trench until you come across a couple of Reaper Leviathan skeletons. From here, if you continue ahead you should end up at the disease research facility. If you keep going downwards, you will end up in a volcanic zone. Keep in mind a juvenile Ghost Leviathan makes its lair near the drop off.
Blood Kelp Trench
This path will take you down the trench and through a short tunnel system. It will deposit you at the central boneyard in the lost river.
The trench is located at the western edge of the dunes biome near three large smokestacks. About halfway down the trench you should see a sizable chunk of shipwreck, that means you are in the right place.
When descending, you do not actually want to search for the deepest point in the trench, just keep going down until you come across some very small brine pools. From there, simply follow the large tunnel to the northeast. Keep in mind the Cyclops will not fit down into this trench.
Blood Kelp Zone
Located north of lifepod 5, the blood kelp zone features a much larger and more visible opening than the blood kelp trench. Just keep going down and you will find your way into the lost river with relative ease.
Deep Grand Reef
The last entrance is located just behind the deep Degasi sea base inside the grand reef biome. Enter the large opening in the cavern wall behind the base and you should see brine pools along the tunnel floor. This path will deposit you at the corridor leading to the Lost River Lab and the Central Boneyard.
Get Rich Quick
Rare resources are plentiful down in the lost river. If you’re going to risk your neck diving down here, you may as well make sure you have something shiny to take home with you. This section will point out some of the best mining spots and how to reach them, as well as a few pointers for acquiring some of the more elusive resources found down in this biome.
Lithium and Crystalline Sulfur
The lost river is easily the best biome for farming lithium and sulfur. But, as you’ve probably guessed, the best stuff is always somewhere dangerous.
You’ll need the Prawn Suit to take advantage of these mineral deposits. Most of the large lithium veins and a substantial quantity of sulfur crystals are located down inside the brine pools you see around.
Since the Prawn is the only vehicle not affected by the acidic brine, it is the obvious choice for exploring the murky depths. You’ll need the drill arm attachment to break down the large deposits, and you may want to add a couple of cargo compartments to your suit so you can carry more.
If you’re looking for a good place with plenty of brine pools to mine, I recommend the central bone field. This boneyard is located right at the center of the biome and has entrances to most of the other points of interest.
The floor of this chamber is about 700 meters in depth. You will know you are in the right place when you see the giant skull and ribcage encircling a few small islands topped with smokestacks amid the brine.
Gold and Nickel Ore
It is possible to find a few lone stacks of nickel and gold ore dotting the rims of the biome’s larger chambers, but your best chance at striking it rich with these resources is also going to be down in the brine. As before, you’ll need the Prawn Suit to get down there and the drill arm to mine the ore.
By now, you’ve probably noticed a few of those “waterfalls” around the edge of the river. Those brine waterfalls often empty into tight caves containing a large concentration of nickel and gold deposits, among other scattered minerals.
If you’re having trouble finding waterfalls, check the outer edges of any larger chambers you come across. You can also follow the river itself to boneyards that will each have at least a few of these waterfalls around their edges. The central boneyard I mentioned in the Lithium and Sulfur section has several waterfalls along its southeastern wall.
Ruby, Quartz, and Lead
Just like in the shallows, quartz can be found in any cramped tunnels you feel the urge to explore. But if you are looking for larger deposits that you can mine with a drill, I suggest you check out a location I call “the basins.”
The basins are located downriver from the central boneyard, near the disease research facility and the entrance to the ghost forest. This section of the river is composed of a series of short brine waterfalls that form a set of stairs leading downward.
In between each set of waterfalls is a short section of river, usually marked with small islands similar to those in the central boneyard, only these have minerals on their surface.
To be clear, you will not find a lot of lead anywhere in the lost river, but most of what can be found is around the edges of these basins alongside quartz deposits. More quartz can be found on the islands in the center near the smokestacks.
This is also where several patches of rubies can be found. In fact, just about any smokestacks you see around the lost river are viable spawn locations for rubies.
Diamond, Magnetite, and Uraninite
Diamond, magnetite, and uraninite crystals can be found in most locations within the lost river biome. Unless you intend to drill at the clusters of uraninite crystals that spawn under the brine pools, you will not need the Prawn Suit to harvest these resources. In fact, the heavy exosuit may prove a hinderance, as most of the crystal clusters you will find will be in elevated locations.
Specifically, look for stalactites hanging from the ceilings of larger chambers, the caves around the tops of brine waterfalls, and the tunnels found in the ceilings of boneyards. These three crystals have the potential to spawn just about anywhere on elevated cave walls, especially in shafts connecting different cave levels.
If you are looking for uraninite in particular, the ghost forest contains the biome’s highest concentration of radioactive crystals.
The sheer quantity of giant skeletons littering the lost river is a good indicator of just how dangerous this biome can be. Down here, there are two major threats you’ll need to deal with: the brine pools and the wildlife.
If you can manage those two threats alongside the ever-present risk of drowning, perhaps you can avoid becoming the next addition to the boneyard.
The Brine Pools
The brine pools of the lost river are a fascinating feature that has lured many an unaware diver to a quick death. The dense, greenish murk is highly acidic, dealing considerable and rapid damage to anything not native to the biome.
Camera drones, vehicles, and especially human bodies will be rapidly eaten away if they should touch the brine. The one exception to this rule is the Prawn Suit.
The Prawn Suit is designed to survive the most extreme environments and is the only method of safely exploring the brine pools without risking damage to yourself or your equipment.
Managing the Wildlife
The most common living threats in the biome are the river prowlers. Skeletal in appearance, it is only fitting that the boneyards should be swarming with these hungry beasts. As frightening as they may appear, river prowlers are not particularly aggressive if you do not present yourself as an easy meal.
They rarely attack if you are inside a vehicle, and I have found myself able to stroll around inside my prawn suit in relative safety. Should a prowler wander too close while you are mining down in the brine, give them a quick smack with your suit’s fist or scrape them up with your drill and they should leave you alone.
The ghost leviathans are a different story entirely. Inside the largest chambers of the lost river, you will find yourself face to face with several juvenile ghost leviathans. Don’t be fooled by their smaller size, these leviathans can still kill an exposed diver in 1-2 hits, with or without the reinforced dive suit.
As long as you are within eyesight of these monsters, they will make a pass to try and eat you each time you draw their attention. Fortunately, they make a very obvious roar before they turn to dive at you.
When you hear them coming, shoot them with the stasis rifle and move out of the way. It will take them a little while to re-orient themselves, especially if you’re next to a wall and they don’t have space to turn around.
If you are intent on wiping out the leviathans within the river, the prawn suit is your best bet. As cool as the poison gas torpedoes are, I haven’t found them to be very effective.
When I’m hunting leviathans, I go with one of two loadouts for the prawn. The first option is the drill arm and the grapple arm. I find this to be particularly effective because it makes you very difficult to hit. Just get close enough to your target to latch onto its side (away from its head) and keep drilling it while it tries ineffectively to shake you off.
The other option is the propulsion cannon arm and a cargo full of deep shrooms. Just load the deep shrooms into the propulsion cannon and you can fire them off like acid missiles.
Points of Interest
Lets get to the real reason you’re down here. There are a number of alien structures located within the lost river biome that are required to move the story forward as well as a few others that contain some cool stuff.
Additionally, there are a few natural formations that you shouldn’t pass up the opportunity to check out for yourself. Note that the sections below will not contain spoilers about what is inside the alien facilities in the region, so no worries.
The central boneyard is, unsurprisingly, located in the centermost chamber of the lost river. The cavern in which the boneyard is located in is the most open area in the entire biome, and contains significant quantities of natural resources.
This location is identifiable by the long stretch of brine river, the tunnel of giant ribs, and the titanic skull dominating the middle.
It is unclear what kind of creature created the skull and what could have killed something so massive. Fortunately for us, it is dead now, so it’s not our problem.
The high concentration of brine pools in this area make the prawn suit a necessity for exploration, and the constant presence of a juvenile ghost leviathan makes sightseeing a bit dangerous. On the bright side, the giant ribcage makes swinging around with the grappling hook a lot of fun.
The passage to all other points of interest can be found down the river from this location.
Sea Dragon Boneyard
This boneyard is dominated by a central, almost altar-like island of rocks surrounded by waterfalls. Lying in the middle of this island is the skeleton of a long-dead Sea Dragon Leviathan. The islands scattered around this relatively small chamber are dotted with numerous smokestacks and chunks of table coral.
While there are some sea prowlers in the area, they mostly stick to the edges and upper reaches of the chamber where schools of spinefish tend to gather. Although, they will sometimes congregate near the sea dragon skeleton, particularly when you first enter.
This boneyard connects directly to the Disease Research Center and the Ghost Forest.
The Ghost Forest
The ghost forest is easily my favorite location in the entire game. This area is absolutely beautiful.
The forest is dominated at its center by the Ghost Tree, a bioluminescent tangle of branches containing the only wild instances of ghost leviathan eggs and surrounded by ghost rays. The blue-colored brine in this area is non-acidic and completely harmless to both you and your vehicles.
The path through the ghost forest is largely flat, marked at the edges by a few smokestacks and littered with deep shrooms. If you are looking for deep shrooms, you can find hundreds of them here.
If you follow the forest path to the end, you will find yourself in the inactive lava zone.
Disease Research Facility
The disease research facility is a story location required to progress to the end of the game. To locate the facility, follow the river down through the boneyards until you spot alien tech hanging from the walls.
Follow the lights through the tunnel until you come across a massive, cube-shaped structure at the center of a chamber.
If you are entering from the tunnel mentioned above, the entrance to the facility will be at the rear of the building or the East-Northeastern side.
Look for a rectangular opening near the top of the structure. Just be cautious, as the area will be guarded by Warpers.
Lost River Lab
The lost river lab (or lab cache) contains several valuable items, including one which you cannot find anywhere else.
To find it follow the tunnel leading into the lost river from the grand reef entrance and take the path with the enormous, unidentified skull at the end of it. From there, look south to find a small doorway blocked by an energy gate.
Note that this gate cannot be opened without an orange tablet. Inside, you can find audio files, scannable samples, and an egg allowing you to hatch an adorable Cuddlefish friend.
Lost River Gate
The lost river gate is located in a small cave behind a waterfall in the sunken portion of the ghost forest.
From the central boneyard, look for a large waterfall with a broad ledge at the top. Beyond that ledge you should see what appear to be lots of small ghost trees sticking out of a mire of green brine.
Follow the swamp back until you see a small waterfall with an alien lantern on either side. Just behind that waterfall is an airlock leading into the cave where you will find the gate.
The gate, when activated, will take you directly to the center of the Lava Castle.
Question: Does the Brine Deal Damage to the Seamoth?
Answer: Yes. The brine deals damage to everything except the Prawn Suit and the wildlife.
Question: What’s with the Blue Colored Brine in the Ghost Forest?
Answer: The blue colored brine is completely harmless. It will not deal damage to you or your vehicles like the green brine does.
Question: Do the Ghost Leviathans Respawn if You Kill them?
Answer: No. Unlike the adult ghost leviathans at the edge of the crater, the juvenile ghost leviathans within the lost river will not respawn if you manage to kill them.