Leviathan, Eater of Worlds

Leviathan, Eater of Worlds is a raid lair in Destiny 2: Curse of Osiris.

Guide
The raid begins on the outer hull of the ship, as with the main Leviathan raid, but a large door opens and allows the fireteam to enter the interior via a different path.

Escape the Reactor
The team arrives in a large flooded room. One by one, a sequence of small platforms will rise out of the water, each one only rising when a guardian steps onto the most recently risen one. Each platform may only be occupied by one guardian at a time; if more than one stands on the same plate then all plates will descend to restart the sequence and any player who touches the water will be killed. Thus, the team must move along the platforms one at a time, only advancing when the player ahead of them advances. There are 4 platform traversal sequences, each of which has a different pattern and leads to different parts of the room. During the sequences, enemies will spawn on distant ledges and fire upon the team.

Defeat the Loyalists
After passing the platforms, the fireteam arrives on a wide ledge on the side of the area. A large number of enemies will begin spawning and the team must survive until Calus invites them to help him with a problem the Leviathan is currently experiencing.

Delve Deeper
As the team proceeds further they will encounter a path snaking through a room filled with large pistons; at points along the path are vertical plates which can shield players. Each time the pistons slam home they will generate a shockwave; any guardian not standing behind a shield will be killed. After passing the pistons, the fireteam will come across a rifled cylinder. This cylinder will periodically seal itself and then "fire" any players inside it into a vast open space filled with floating debris. As they fall through this space, they can angle themselves to pass through a series of rings; if all six rings are activated a loot chest will spawn at the bottom of the descent.

Break the Barrier
Floating in the center of the Leviathan, within a forcefield, is a large Vex construct ringed by floating platforms. There are three charging stations on the platforms, one for each element, and points where Vex head pieces ("skulls") periodically spawn. Each charging station features three devices which can convert a skull into a cannon which a guardian may pick up and use to fire a beam of the corresponding element. Picking up a skull will begin the encounter and cause enemies to begin spawning throughout the arena.

The central construct, Argos, will spawn three quantum mines on one of its sides, facing one of the stations. Each of the mines will be charged with a random element, and the face on which the mines appear will also be chosen at random. These mines can only be damaged by the cannons, so once the combination of mines is known the fireteam must gather skulls, deposit them in the corresponding charging stations, take the produced cannons to the side where the mines are, and shoot them off to disarm them. One cannon carries enough charge to disarm one mine and heavily damage a second, but in general the same number of cannons must be produced as mines that have spawned.

Once all 3 mines have been disarmed, the construct will be damaged and a new set of mines will appear. As the fireteam completes cycles the construct will take visible damage and pieces will fall away, revealing a large Vex entity within it. After the construct is completely destroyed a loot chest will spawn.

Argos, Planetary Core
The final encounter of the lair may be triggered at this time. Argos is a large Hydra protected by an impenetrable shield, which may be damaged by a procedure similar to that used in the previous encounter.

Again, Argos will spawn 3 elemental charges on a random side of its shield, and again, players should gather and produce corresponding cannons. When an energy charge is shot with a cannon, it will slide along Argos's shield towards a receptacle in the center. 3 guardians must synchronize so that all 3 charges are pushed into the receptacle at about the same time, which collapses the shield around it. Argos may be damaged at this point, both with conventional attacks and with any remaining cannons (well-coordinated fireteams can produce additional cannons specifically for doing additional damage during this phase).

Argos restores its shield and generates 3 more charges, but they may be ignored at this point. After a short time a message will appear indicating that Argos is overloading, and then the boss rotates quickly before its shield collapses entirely and a set of circular platforms appears around it.

There are six vulnerable points on Argos's body: two on the top of its head, two on the back of its upper body, and two on the sides of its middle "arms". Two of these points must be destroyed in order to interrupt the attack Argos is preparing at this point; it is important to destroy exactly two and no more so that Argos can be interrupted on subsequent phases. After destroying two points Argos's head may be attacked for additional damage until its shield is restored and the entire cycle starts over.

Argos must be killed within 4 cycles, once all of its weak points have been destroyed there is no other way to prevent a wipe.