Horizon Forbidden West – ‘The Sea Of Sands’ Walkthrough

The Sea Of Sands is a mission in Horizon Forbidden West. It’s one of three quests that is accessible after rebooting GAIA, and it sees Aloy venture south to Las Vegas in search of the Poseidon sub-function.

Mission Name	Recommended Level	New Tools	Machines	Rewards
The Sea Of Sands	22	None	Burrowers Longlegs Bellowbacks Glinthawks Snapmaws Tiderippers	17,600 XP 2 Skill Points

Head To Las Vegas

Whenever you’re ready to begin this mission, head to Las Vegas, which is located to the south of the game’s map. Upon approaching it, you should find a large open space with glass-like flooring, indicating a dome underneath. Your objective will be to find a way underground into the dome, and you can do so by searching for a Pagoda-like building known as The Tower Of Tears.

Climb up the tower and approach a tarp. Enter it to trigger a cutscene in which you meet a group of Oseram delvers. Once you’ve spoken to the delvers, you’ll receive two objectives; recover the compressed air capsule and gather machine parts.

Immediately after the conversion, head towards the elevator shaft and dive into the water. Continue diving until you reach a makeshift elevator, and grab the compressed air capsule. Once you’ve picked it up, immediately resurface to avoid dying from the lack of oxygen.

From there, leave The Tower Of Tears and head to the location of the machine herd. They won’t be there, but you can use Aloy’s Focus to follow their tracks. On your way, you’ll run into a machine herd with Burrowers, Glinthawks, and Bellowbacks. Defeat the machines, and once you’re down, follow your objective and scan your Focus to pick up more tracks.

Follow the tracks to a new herd of machines, including Bellowbacks, Longlegs, and more. Once you’ve defeated all of the machines, loot them to acquire their parts, and then head back to The Tower Of Tears to speak with Morlund. After the brief cutscene, head to the nearby workbench and craft the Diving Mask, allowing you to dive into water without worrying about Aloy’s oxygen levels.

Explore The Ruins Underneath Las Vegas

With your new Diving Mask, head back to the elevator shaft and dive into the water. Your new objective is to find Poseidon in the ruins under Las Vegas, and you’re now free to explore deep underwater environments. Swim to the bottom of the elevator shaft and then through the open door at the bottom. Explore the room it opens up to, as you’ll find several datapoints detailing the accomplishments of Stanley Chen.

Once you’ve explored the room, follow your objective marker through a pair of doors to get your first glimpse of Poseidon’s handiwork in the underground ruins. Dive deeper and then push forward through a set of doors that opens up to an underground Las Vegas city. While doing so, you’ll be greeted by a Tideripper.

If you push forward, you’ll see the Tideripper swimming. Avoid it and instead turn right and dive to the ground, where Aloy will make note of the flashing red light witnessed by Morlund and friends. Approach the console, and you’ll receive a new objective; drain the city. To do so, you’ll need to find and activate the two Pump Nodes found in the ruins.

Activating The Pump Nodes

The Primary Pump Node can be found by leaving the console, taking a left, and swimming directly ahead. You should notice some Stealth Kelp, so make sure to hide in the plants to avoid alerting the nearby Burrowers and Snapmaw. If you follow your objective, you’ll find a small opening in the ground. Dive in and follow the tunnel along, leading to another room. At the far end of the room, you should find a ladder Aloy can use to access the walkway and the Pump Node – this might require you diving once again and swimming under a large wall.

When you reach the walkway, follow it along to a hologram of the Vegas ruins. Opposite the hologram is the Primary Pump Node. Open it, and to your left will be some Firegleam you can ignite for some resources. Turn back around, and head past the Pump Node to dive back into the water. Make your way back to the ruins.

From the opening in the ground, swim straight ahead and take note of any nearby machines. Use the Stealth Kelp as cover, and follow your objective northeast towards another opening in the ground, just past a Burrower. Dive into the opening, and then swim along the tunnel until you reach another ladder. Follow the walkway along until you reach a second ladder, and then perform a running jump to access the other section of the walkway. Beside it will be some Firegleam you’ll need to ignite in order to open the secondary Pump Node.

Once you’ve activated both Pump Nodes, swim back out to the ruins, and your next objective will be to find and activate the Pump Maintenance Station. From the opening, the station can be found northeast of your location in a large tower. Swim in that direction while avoiding the machines, and then swim around the base of the tower until you see an opening.

Swim into the opening, and dive. You should see a Greenshine Cluster, so grab it. Open the nearby set of doors and then pry open the next set. Continue swimming ahead and follow the hallways around. You’ll eventually reach a large dome-like room, swim up and access the nearby console to drain the city and trigger a cutscene.

Find Poseidon

With the city drained, you’re free to explore it on foot. Make your way back to where the Tideripper originally was, sneaking past the Snapmaws and Burrowers. When you reach the location, a cutscene will play reuniting Aloy with the Oseram delvers. As this happens, the Tideripper will emerge and you’ll need to defeat it to continue with the mission.

The Tideripper is a gigantic machine, and it has several ranged attacks that can repeatedly stagger Aloy, making for a frustrating fight. However, the Tideripper is weak to Freeze and Shock damage, and comes with two Purgewater Sacs that can explode when dealt enough damage. While fighting it, the Oseram delvers will also help.

Once you’ve defeated the Tideripper, watch the cutscene and head towards the doors it was guarding. Once through, follow the hallways around, descend a staircase, and pass through another set of doors that open up into a large data room. Head to the far side of the room – pick up the datapoints on the way – and interact with the nearby console to retrieve Poseidon.

Now you’ve got Poseidon, it’s time to head back. Return to the underground ruins of Las Vegas for a sweet surprise, and then climb the tall ladder and head back through the nearby building to access the elevator shaft and head back to the surface. When you leave The Tower Of Tears a cutscene will play, and you can fast travel back to the Base.

When you’re back at the Base, a cutscene will play and you’ll receive your final objective; speak with GAIA. Head to the control room and speak with GAIA to merge her with Poseidon and complete the mission.

Previous mission: ‘The Eye Of The Earth’
Back To: Horizon Forbidden West Mission List
Next mission: ‘The Cradle Of Echoes’