2 bosses, shared health pool.
Most important ability in this fight is torment. It will be a bar in the middle of your screen. Once it reaches 100, you will deal 20% less damage, take 90% more damage, have your hit chance reduced by 90% and receive 25% less healing.
You gain torment from the bosses abilities.
You can get rid of all the torment you have by using your extra action button. Using it, you will go up and into another room where you will fight a tormented soul add. This add will melee whoever has threat, spawn green swirls that deal damage to anyone standing on them. While you fight the add, he will spawn orbs that when you walk over them, you will lose 35 torment. At 0 torment, you will be able to use your extra action button again and be ported back into the main room.
Recommended to keep one tank inside the cage room at all times. The add doesn’t do much damage, so you won’t need a healer in there. Once the main tank needs to go into cage, have everyone leave the cage and then the new tank go inside. Possibility of 3 tanking the fight, as well.

THE TWO ADDS
Atrigan
Face away from raid.
Bone Scythe - passive that says his melee attacks apply 2 torment
Scythe sweep is a frontal cleave that deals damage and applies 20 torment.
Calcified Quills - targets a players then does a shockwave towards them that knocks up and deals damage to anyone in its path. Usually always hits the tanks. So no one else stand on the tanks.
Bone Saw (signature ability) - Spins around really fast and deals damage to anyone who is around him and applies a lot of torment to anyone who is attacking him during this duration, so make sure all DPS switch to Belac. Tank kite the boss away from Belac.

BELAC
CANNOT BE MOVED. Interrupt order on Belac for his ability: Pangs of Guilt. If it goes off it deals huge raid wide damage.
Suffocating Dark - Will create a void zone on top of 3 players that slow and give anyone standing in them 8 torment each second, as well as damage.
Echoing Anguish - debuff that does ticking damage and applies 2 torment every second for 12 seconds. Once dispelled (or time runs out) anyone within 8 yards gets 10 torment. So wait for whoever has the debuff to be out of range of other players before dispelling. (THIS CAN TARGET MELEE)
Tormenting Burst - Will Deal a flat amount of 8 torment to all players and high damage.
Fel Squall (signature ability) - Deals damage and applies torment to players near him and anyone attacking him during this duration, so all DPS should switch to Atrigan.

Ranged will want to avoid standing at the entrance to the room because those leaving the cage will spawn there and you don’t want them to spawn into void zones.

Video of Fight!