This fight is awesome. The boss is active the whole time, there are three distinct phases, and there are actually some pretty unique mechanics.
There are a lot of abilities in this fight, but ultimately each phase boils down to one ability that will wipe you quickly if not dealt with appropriately. For Phase One, it’s spreading for item. For Phase Two, it’s getting item way out of the raid, and for Phase Three it’s catching the item.
This is mostly a single-target fight, with infrequent burst aoe in the first phase and two-target cleave in the second phase. We recommend using Bloodlust in Phase Three once the orb is caught the first time.
Keep the boss faced away from the raid at all times, because he will occasionally hit the tank with a combo of abilities including a frontal cone (item -> item -> item). The tanks should immediately taunt swap after this combo.
Stand in the safe zone of each eruption of item. A giant purple circle will spawn 3 times in a row centered on where the boss initially cast it, and there will be a different safe zone for each circle. This can overlap with any of the other mechanics in the fight.
Stay spread while item is going out or else it will basically one-shot people. Several of these will go out in a row and then stop for a few seconds.
A big group of small adds will spawn occasionally at a set location. These adds ignore threat and fixate random players. All stuns, slows, knockbacks, etc. work on these adds, so just group them up and nuke them.
At 65% health remaining, these mechanics end and Phase Two begins.
A green debuff (item) will occasionally go onto a random player. This debuff needs to be taken WAY away from the raid by the time it expires. It drops a green cloud on the ground that slowly drifts around the spot it was dropped for the rest of the fight. Everyone in the raid should avoid these clouds at all costs, because they spawn a nearly raid-wiping add when touched (item).
Three big adds spawn occasionally at separate locations. They all spawn at the same time, and the two furthest from the boss should be hard cc’ed immediately. Kill the adds one by one and keep them interrupted. Start with the closest add to the boss and move the boss on top of each one as you kill it.
At 30% health remaining, these mechanics end and Phase Three begins.
A purple orb will start slowly falling from the ceiling in the middle of the room (item). This orb needs to be soaked by one player as it hits the ground. It will then continue to bounce around the room for the rest of the fight, needing to be soaked by a different player as it hits the ground every time. Soaking the orb gives that player a huge buff for 30 seconds, and then mind controls the player and causes an 8 yard explosion around the player (item). This mind controlled player needs to be interrupted and killed.
An additonal orb will be added about every minute after the phase begins. This acts as a soft enrage, as you will quickly run out of players to soak the orbs. Bloodlust shortly after this phase begins and nuke the boss.
Don’t stand in front of the boss. Stand in the clear zones of the occasional giant purple circles.
Spread out for Eye Beam. Kill little adds.
Get green debuff to wall away from raid. Kill and interrupt big adds on boss. Avoid green clouds.
Soak purple orb when told. After soaking, get out of raid right before debuff expires. Avoid green clouds.
Other than Surging Darkness that happens occasionally throughout the fight, everyone only really needs to worry about one mechanic in each phase. In Phase One, spread out while Eye Beam is happening. In Phase Two, get Roiling Deceit way out of the raid and avoid those clouds. In Phase Three, catch the orb every time and kill the mind-controlled players. Everything else is baby stuff.
The triple-hit combo from the boss hits REALLY hard, so plan on using at least one major defensive cooldown in addition to your active mitigation for it. This combo happens about every 35 seconds. It is incredibly important that the taunt swap happens immediately after the last hit of the combo, as the current tank can’t be healed for 8 seconds.
The tank combo can happen while dodging the giant purple void zone, so try not to point the boss at anyone.
There are adds in the fight, but none of them can be tanked. The off-tank should help cc the little adds and interrupt the big adds, but always be ready to taunt swap at the end of the tank ability combo.
This fight has a lot of consistent raid damage. Assigning healer cooldowns for each Surging Darkness could help a lot, as it pulses damage to everyone and a lot of movement is required at the same time.
Make sure the boss tank is topped off for each hit of the tank combo. The tank will take 50% reduced healing after the first hit, then take a huge second hit, and then can’t be healed for 8 seconds after the third hit.