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In order to sever the connection of Emperor Calus and The Lunar Pyramid, Eris Morn had invited The Guardian, Crow, and Commander Zavala to take place in a ritual that would expose their deepest fears and regrets in the form of Nightmares. The Sever missions follow Crow, Zavala, and Empress Caiatl as the Guardian helps them combat their Nightmares and weaken Calus's grasp over the Pyramid.
There are six Sever missions in total, two missions per character. Each pair of missions share similar mechanics gameplay-wise.
Sever: Shame / Sever: Reconciliation
Sever: Shame and Sever: Reconciliation follow Crow and the confrontation with his nightmares, the Nightmare of Uldren and the Nightmare of the Fanatic. Crow feels shame and anger towards his past list as Uldren Sov and his role in the creation of the Scorn and during Sever: Shame, he makes it clear that he wants no part of Uldren within him. This mentality ultimately leads him to fail the severance ritual. In his return to the Leviathan in Sever: Reconciliation, Crow manages to overcome the Nightmare of Uldren by accepting that Uldren will always be a part of him, but he will not become Uldren if he learns from his mistakes.
The missions begin with the player spawning in the Leviathan's Underbelly. Walking forwards will reveal that the door is currently locked but can be opened if the player looks up and shoots the sparking blue fuse. Behind the door will be a place where the player will plant a Ritual Amplifier. Moving forwards, the guardian will see a tube that they must go through but is blocked by a wall of Arc energy. There is a door to the left that stutters open and shut but walking next to it will cause the door to open, revealing more fusing that can be shot, dropping the shield once the fuses are destroyed. The tube leads to a small maze section. One of the solutions is as follows: Left - Right - Left - Right - Straight.
After the maze, the player will enter the Armory, where they will be blocked by a wall of Darkness energy and a pod of Egregore spores. Standing near the spores and destroying them grants a small buff that allows the player to pass through the wall. The player will then be tasked with clearing out the Armory of Cabal Loyalists, after which the power will shut off and more Cabal will spawn. After killing off the Cabal and their commander, Val Dumoar Sentinel Commander, the player can make their way forwards where they can see Crow and the Nightmare of Uldren behind a large window. Crow and his Nightmare will have some dialogue before a large door to the left will open, revealing a lever which will restore power when pulled. This will spawn a small wave of Psions. The player will now be blocked by another wall of Darkness energy. There will be another blue fuse within the Armory that can be shot, opening a door which reveals another pod of Egregore. Making their way past the wall of Darkness, the player will go through a small incineration tunnel.
Crawling through the tunnel, there will be another location to place a Ritual Amplifier. The door will open and players will find themselves in a room with a small group of Cabal and a lever marked by a quest indicator. Pulling this lever brings down a lockdown and spawns in a large, invincible Ceremonial Bather named The Contaminant. Players will have to avoid the Contaminant as they find four levers around the room to lift the lockdown. One lever will be blocked by a large wall of Arc energy, so the player will be forced to carry a large Wrench that slows their movement speed and lowers their jump height. Once carrying the wrench, they will carry it to a node that needs to be repaired and once repairs, the arc wall will drop and the player can pull the final lever and escape.
The player will make their way into a small room of Scorn and listen to some more dialogue between Crow and Uldren. There will be a place to plant another Ritual Amplifier and a door that is locked by another fuse. The player will navigate their way through to a large fan lift that will take them to The Gauntlet. They will listen to some more dialogue before beginning the ritual. The Nightmare of the Fanatic will spawn in and allow the player to damage them before escaping into the Gauntlet's running course. The player will follow through a portal which will take them into the running course and a battle with the Fanatic will ensue, will waves of Scorn attempting to impede progress. During the fight, The Fanatic will periodically teleport and run away and if the player cannot kill the Fanatic before it reaches the end of the course, the player will be teleported out.
If the player is teleported out, the player will be swarmed by waves of Scorn. Killing all of the Scorn will make the portal reappear and the fight with the Fanatic can resume. Killing the Fanatic will teleport the player out of the running course and the mission will end after some more dialogue.
Sever: Grief / Sever: Forgiveness
Sever: Grief and Sever: Forgiveness follows Commander Zavala as he tackles his nightmares, the Nightmare of Safiyah and the Nightmare of Kethiks, Grief Unforgiven. During the events of Sever: Grief, it is revealed to the player that Commander Zavala's Nightmares are built upon guilt regarding the death of his son Hakim as he feels that he was directly responsible for Hakim's death at the hands of Kethiks, the Yet-Proven. It is further revealed that this guilt also extended to Guardians under his command and his wavering devotion to the Traveler. Due to this guilt, he fails the first severance ritual but returns to the Leviathan in Sever: Forgiveness. He manages to overcome the Nightmare of Safiyah by forgiving himself for Hakim's death. When he mentions his thoughts of the Traveler, the now Memory of Safiyah urges him to rest instead.
These two Sever missions have different beginnings. In Sever: Grief, the player spawns in near the underbelly of the Royal Gardens and will make their way forwards and find their way blocked by a current of Arc energy that covers the next room that will kill them if they step into it. The way forwards is behind the player and after making their way through the corridor will find themselves in a garden filled with plants in large pots that is guarded by a small group of Scorn and War Beasts. Pressing onward, the player will find a place to place a Ritual Amplifier which will open the door forwards. The player will find themselves back at the room covered in Arc energy with a small pod of Egregore and door blocked by Darkness energy. Destroying the pod while standing near it will allow the player to pass through the door and find a large Wrench at the end of the hall. A small group of Scorn will spawn when the Wrench is picked up. The player will then take the wrench up into the pipes that hang over the Arc energy room and navigate their way back to where the Egregore pod is. They can interact with a node with the Wrench in hand to disable the Arc energy field. The player can then walk through the room and interact with a console to move forwards.
In Sever: Forgiveness, the arc energy field is disabled. However, the console used to move on will be deactivated. The player will have to make their way over to the Wrench once more to carry it over to a node that will reactivate the console. There are small groups of Scorn within the rooms that will attempt to impede progress. Once the player has made their way past the console, they will encounter a room that is filled with Scorn and Cabal. Clearing this room will cause more Scorn and Cabal to spawn once the room is cleared. When all the Scorn and Cabal have been killed, there will be another spot to plant a ritual amplifier before moving upwards to meet up with Commander Zavala and the Nightmare of Safiyah. Zavala and his nightmare will have some dialogue before the doors open, revealing another place to plant a Ritual Amplifier. Moving on, the player will find themselves in a cylindrical room with a Egregore pod and a tunnel blocked by Darkness energy. Crawling through the tunnel will lead to a drop into the confrontation with the Nightmare of Kethiks.
After some dialogue between Zavala and Safiyah, the player can begin the ritual. Kethiks will spawn in with waves of Fallen to support it. Dealing one-third of its health will cause it to go immune and disappear. More Scorn and Fallen will spawn in and once enough enemies are defeated, Kethiks will reappear. This mechanic will repeat once more when the next third of its health is dealt. The mission will end after some more dialogue.
Sever: Rage / Sever: Resolve
Sever: Rage and Sever: Resolve follows Empress Caiatl as she attempts to tackle her nightmare of Dominus Ghaul. Caiatl has surged ahead to take her nightmare head on without participation in Eris's ritual, leading The Guardian to rush after her and help her defeat her nightmare. Caialt feels rage against herself for the loss of Torobatl at the hands of Xivu Arath, God of War and the subsequent fleeing into the Sol system. She is conflicted and angry about the alliance with the Vanguard as her mentor, Ghaul had defeated them. This anger at herself and inner conflict leads her to fail the severance mission the first time. In her return in Sever: Resolve, she overcomes her nightmare by realizing that she has made her own legacy of success and does not need the approval of the past to keep going. She concludes that she has made the Cabal change for the better under her leadership.
The missions begin in the Leviathan once more, with the player making their way through winding corridors that are lightly guarded by Cabal. Fighting their way through the Cabal, the player will eventually meet up with two of Caiatl's forces, Val Parthus, Coalition Ally and Bracus Lume, Coalition Ally, a large Incendior and Legionary respectively. The player and the two NPCs will fight their way through waves of Scorn and Cabal to a point where the player can plant a ritual amplifier.
In Sever: Rage, the player continue forwards to find the way down blocked by another wall of Arc energy. In order to disable the wall, the player will move forward into the next room where they will find the Hammer of Proving and two fuses over the doorway which will drop the arc wall when destroyed. In Sever: Resolve, the player will instead listen to some dialogue between Caiatl and the Nightmare of Ghaul before the arc wall drops. Either way, the player will need to make their way down into the next room where they will find the way forwards blocked by large moving fans. Players will go into a room to the side of the drop and see a console that when interacted with, brings on a lockdown and spawning in the Contaminant again. To the immediate right of the player there will be a fuse to shoot which opens two doors ahead. Behind the doors is a hallway with a lever which when pulled, opens the door to the incineration room. The player will then lure the Contaminant into the incineration room by leading the Bather down the ramp that can be found near the back of the initial room, past the room full of gold, and into a hallway. The player will then jump up and pull a lever which will burn away the Contaminant.
The player then can interact with the console once more and the lockdown will be lifted and the large fans will stop. The player will also be joined by Optus Ulios, Coalition Ally, a large psion. The player with the three Cabal will fight their way forwards to Caiatl, who will be waiting to start the ritual. After some more dialogue, the fight with the Nightmare of Dominus Ghaul will begin. Ghaul will first spawn in on the ground. After a few moments, he will unleash a burst of Arc energy and begin to fly away. Ghaul will continue to alternate between flying and staying on the ground until the player kills him.
The mission will end after some more dialogue between Caiatl and the nightmare.