Leviathan Reef Base

From the starting point, pull the switch. Return to the path before the Botanical Garden and head right into a pipe on the ceiling. Rip off the grid and proceed right to reach the flashback room.

Swim to the surface and enter the path on the right. You'll return to the room with the lasers. Pass through them while invisible and squeeze through to reach the Leviathan Reef Base.

Descend through the water-filled rooms, proceeding to the right.

In the next room, defeat the enemies, using the environment if possible. Pull the switch to open the gate below and proceed right.

Defeat the enemies in this area and consume them to evolve to your second form. Break the wooden walls on the right, then take the path to the left.

You will return to the previous room. Pull the switch to open the gate and deposit biomass into the pool of red liquid. Return to where you broke the wooden walls and use a web sling on the lever to open the gate. Defeat the enemies, retrieve biomass, enter the door, and go through the pipe below.

To deal with the armored soldiers, you can charge through the wooden wall to kill them. If in your first form, you can become invisible to defeat them safely. Be aware of their flamethrowers. After defeating them, proceed to the pipe. You'll see the Relith sign just before the rivet; remember this location. Proceed left.

Follow this path straight to the end and pull the switch. Enter the unlocked path to the next room.

Activate the hive and save. Defeat the enemies, being careful of the armored ones with flamethrowers. Proceed right, then keep to the right in the next room.

Activate the second hive to open a path. Quickly go downwards, grab the drone, and destroy it to unlock the gate below. Advance to the next area.

Defeat the enemies, prioritizing the normal ones on the right, then the armored ones on the left. Consume some enemies to grow to your second form. Charge through the vent to proceed.

In this area, break the containment unit and squeeze in to consume the sample and get the Hidrophilia upgrade. This allows you to become a swarm of worms in water and pass through grated walls.

Head upwards to the room with the last hive. Activate it, then go left to the next room.

Face the Dreadnought. Attack it from behind by charging or by grabbing with tentacles and running away to remove its machine gun pieces. Once the human inside is exposed, grab and kill them.

After defeating the Dreadnought, the gate will open. Head downwards through the grated wall to reach the unsealed door to the Frontier Marshlands.