After defeating the Amalgamation Chamber players will gain access to the Forgotten Experiments’ room. This is a 3 boss fight, however players will face one boss at a time so it will not be an AOE fight.
The first boss players will face is Neldris, and her melee attacks are empowered by Infused Strikes. This causes his melee attacks to inflict arcane damage every second, this effect stacks. Touching another player afflicted by Infused Strikes removes all applications and causes an Infused Explosion. This inflicts arcane damage to all players and puts a dot on them that deals arcane damage every 2 seconds for 20 seconds. Tanks will need to carefully manage this mechanic throughout the fight, and all the bosses use Infused Strikes as their tank mechanic. Healers should watch when tanks clear their dot, as Infused Explosion going off at a bad time could pick off low health players.
Neldris will target several players with Rending Charge, then she charges between them. Anyone caught in her path takes physical damage, gets knocked back, and gets a bleed that deals physical damage every second for 15 seconds. This effect stacks. Players targeted by Rending Charge should stand still and let others move out of the way, or go to designated spots to avoid getting other players hit.
Her next ability is Massive Slam, this is a frontal cone that deals physical damage to any players caught in it. Neldris will face a random player when she casts this, so it cannot be aimed. The final ability Neldris uses is Bellowing Roar, this deals arcane damage to all players and players that are farther away take less damage. Players should use defensives if they cannot get away from Neldris fast enough, and save movement abilities for this cast. Healers also need to watch player health and keep an eye on anyone closer to Neldris when the cast finishes.
When Thadrion comes out tanks need to continue to manage Infused Strikes and Infused Explosion.
Thadrion puts a dot called Unstable Essence on random players, this deals arcane damage every 2 seconds and grows in intensity over time. Upon removal the energy explodes dealing arcane damage to all players within 16 yds, this is shown by a large circle that all players should move out of ASAP. A lingering trace of energy then jumps to a nearby player and applies Unstable Essence. Since this dot never goes away while Thadrion is alive, healers will need to coordinate dispels to keep Unstable Essence under control. Ideally the player with Unstable Essence will move out of the raid before he gets dispelled. I can see groups placing down a marker that players will run to when they want to be dispelled.
His next ability is Volatile Spew which spawns arcane globules that will land in the area, where they will land is shown by swirls. Anyone standing on their landing locations will take arcane damage. Players should move away from these swirls as soon as they spawn. Thadrion's last ability is Violent Eruption which deals arcane damage to all players every second for 8 seconds. Healers will want to make sure to not dispel any Unstable Essences during this cast, and major CDs may need to be used during this cast.
Rionthus continues to use the same tank mechanics that Thadrion and Neldris used. Tanks should continue to manage Infused Strikes as they did with the previous bosses.
Rionthus has a lot of Evoker abilities to use against players. His most deadly ability is Deep Breath. Rionthus will jump to the side of the room and target a section with Deep Breath. When the cast finishes he flies across the lab spewing molten cinders below him, any players caught in his path take volcanic damage every 0.5 seconds. When he reaches the other side of the room he will land, choose another section of the room to target, and casts Deep Breath again. Players need to move away from the targeted area ASAP, getting caught in Deep Breath can easily kill players.
His next ability is Temporal Anomaly, when cast he spawns a glowing golden orb that will move towards him. This looks very different from Preservation Evoker's Temporal Anomaly so players will not confuse them. If the anomaly collides with Rionthus he gains a shield that absorbs damage equal to 5% of his maximum health. If a player collides with it then they take arcane damage and it is knocked away. Players must make sure this does not reach the boss as the large absorb shield could result in a wipe.
Disintegrate is his last ability, he will target several players and focuses Spellfrost damage on them every second for 3 second. The magic lingers slowing affected players by 30% and causing them to inflict Spellfrost damage every second to players within 5 yds for 16 seconds. Players targeted by Disintegrate should spread and will have a circle placed on them when Disintegrate ends. Other players should make sure to avoid standing near these players.
In Heroic there is an added effect to dispelling Thadrion's Unstable Essence. An Erratic Remnant is formed when Unstable Essence is removed and Unstable Essence persists after Thadrion’s demise. These Erratic Remnants will keep casting Erratic Burst until they are killed, this deals raid wide arcane damage. When Thadrion casts Violent Eruption all Erratic Remnants will also deal arcane damage to all players every second. It will be important for DPS to kill these ASAP, and healers must be cautious if multiple remnants are active when Violent Eruption goes off.
In Mythic the next boss will join the fight when the current boss reaches 50% health. This will make the fight more challenging as players will need to deal with abilities from two bosses, which could make for some bad overlaps.
The next major change is the bleed applied by Neldris’ Rending Charge is now permanent. This makes it much more important to have no extra players hit by Rending Charge. Some classes will be able to remove the bleed through abilities such as Mage's Ice Block, and Dwarves can use Stoneform to remove the bleed. Evokers will be a handy class to have as they are the only class that can dispel bleeds.
The next change is to Rionthus' Temporal Anomaly. Players hit by Temporal Anomaly gain Temporal Fracture for 20 seconds. This increases all damage they take from Temporal Anomaly by 100%. This will force players to take turns pushing back Temporal Anomaly.
There is everything you need to know about the Forgotten Experiments abilities and how to handle them in Aberrus.