After players defeat Kazzara the Hellforged they are given a choice to go left or right. Players that go left will face the Amalgamation Chamber as their next challenge. This fight starts off with two bosses, the Essence of Shadow and Eternal Blaze. Most classes will go single target for this fight, since the bosses will be separated. Some ranged classes may be able to take advantage of two target cleave builds if they can stay in range of both bosses. The first boss we will look at is the Essence of Shadow.
Essence of Shadow
When one of the bosses reaches 50% health they will merge into the Shadowflame Amalgamation. Players must DPS both bosses evenly to ensure that when they combine, the health of the boss is as low as possible.
The Essence of Shadow pulses every 5 seconds and applies a stack of Corrupting Shadow to all players within 50 yds. This dot inflicts shadow damage every 5 seconds and reduces maximum health by 1% for 20 seconds. This effect stacks. Players should try to only be within 50yds of one boss, as the Eternal Flame has a similar stacking dot mechanic. Anyone with this dot has a purple orb over their head so other players can easily tell who has which dots. Healers should keep an eye on this because the reduced max health will cause players to take more damage than expected throughout the fight.
Shadow Spike is a tank buster mechanic that inflicts heavy shadow damage. It does not apply a debuff so no tank swap is needed, just defensives and active mitigation as stacks of Corrupting Shadow get higher.
Next up is Coalescing Void, this creates a mass of dark energy that inflicts heavy shadow damage to players within 50 yds when it detonates. Players farther from the detonation receive less damage. This looks like a large shadow orb with a spherical effect to show its range. Players that get out of the effect will avoid damage.
The last ability is Umbral Detonation, this is a debuff placed on random players. After 6 seconds each player erupts inflicting shadow damage to all players within 8yds and creating Lingering Umbra. This is a dark residue left on the ground that inflicts shadow damage every second to players standing within it. Players should try and drop this to the side of the room to keep the main area clear.
The Eternal Blaze pulses every 5 seconds applying Blazing Heat to players within 50 yds. This dot inflicts fire damage every second and stacks. Players with this dot have fire orbs above their heads. Healers should keep an eye on this as the damage will ramp up the longer this phase goes on. Players can get both Corrupting Shadow and Blazing Heat, so positioning will be very important in this fight. Its tank buster mechanic is Flame Slash, which inflicts heavy fire damage. Active mitigation or defensives should be used when this ability is cast.
The next ability is Fiery Meteor, which inflicts deadly fire damage split evenly among all players within 8yds of the impact location. If Fiery Meteor does not hit any players it will detonate and inflict fire damage to all players. Everyone fighting the Eternal Blaze should stack for this to evenly split up the damage.
Swirling Flame is the Eternal Blaze's final ability. This launches three Swirling Flames at a nearby player that inflicts heavy fire damage to players caught in its path. Swirling Flames look like fire tornados and travel in a straight line. Melee dps should watch out because the flames will spawn in front of the boss, so as soon as you see the fire move out of the way to avoid getting hit! Players fighting the Essence of Shadow should also look out for these, as they can travel pretty far before despawning.
When the two bosses begin to combine they each start channeling an ability, and slowly shrink until they combine. The Essence of Shadow casts Splintered Shadow and the Eternal Blaze casts Splintered Flames. Both abilities spawn large swirls around the area. Anyone hit by the purple swirls takes shadow damage, and anyone hit by the orange circles take fire damage.
When the bosses merge into the Shadowflame Amalgamation they don't just combine forms, they also combine their abilities into one. The Shadowflame Amalgamation will pulsate every 10 seconds applying Shadowflame Contamination to all players. This is a dot that deals Shadowflame damage every 2 seconds and reduces maximum health by 1%. This effect stacks and puts a Shadowflame orb over player's heads.
The tank buster mechanic turns into Withering Vulnerability. This inflicts heavy physical damage to their target and increases their Shadowflame damage taken by 200% for 10 seconds. Tanks will need to taunt swap after each application. Tanks will also have to watch out for Shadowflame Burst. This is a frontal that follows the bosses' current target, it should be aimed away from the raid. Anyone hit by this takes heavy Shadowflame damage.
Next up is Gloom Conflagration which is a combination of Coalescing Void and Fiery Meteor from the previous phase. This calls down a dark meteor inflicting deadly Shadowflame damage split evenly among all players within 8yds of the impact location. If Gloom Conflagration fails to hit at least 5 players, it detonates and inflicts Shadowflame damage to all players. The impact creates an orb of energy that detonates shortly afterwards, inflicting Shadowflame damage to all players. Players farther from the detonation point receive less damage. Like with Coalescing Void players can run out of the area of effect to avoid the damage.
The Shadowflame Amalgamation will put Blistering Twilight on random players. After 6 seconds these players explode dealing Shadowflame damage to players within 8yds and creating Engulfing Heat which remains on the ground. Anyone standing in Engulfing Heat takes Shadowflame damage every second. Each target also erupts with Swirling Shadowflame, which are Shadowflame tornados basically that shoot out of the player. Anyone hit by Swirling Shadowflame take damage and get knocked back. These players should position to drop Engulfing Heat out of the way, and try not to hit each other with the Swirling Shadowflame that shoots out of them.
If the bosses are within 25yds of each other they will gain Elemental Instability, which increases all their damage done by 200%. Tanks will need to make sure to always keep the bosses apart
The Essence of Shadow gains an additional ability called Shadow Convergence. This spawns orbs of darkness that converge on the Essence of Shadows’ location, any players hit by these orbs take heavy shadow damage. To avoid the orbs, the tank should relocate the boss from its current position because the orbs don't follow the boss. Instead, they always target the spot where the boss was initially when Shadow Convergence was cast. Melee DPS should be cautious as the orbs get harder to avoid the closer the get to their destination.
The Eternal Blaze gains an additional ability called Molten Eruption. This will call down fireballs at nearby locations, where they will land is represented by glowing fire circles. If at least one player is in the circle it will stop glowing. Any players standing in the circle when the fireball lands will take fire damage. The effect of the circle changes when a player stands in it so others can easily tell which one still needs to be soaked. If any fireball fails to hit a player then the entire raid will take fire damage.
In phase 2 the Shadowflame Amalgamation gains the ability Convergent Eruption. This is a combination of Shadow Convergence and Molten Eruption from the previous phase. The boss calls down fireballs at nearby locations, where they land is shown by circles. Anyone within the circle when the fireball lands take Shadowflame damage. If any fireballs fail to hit a player, then all players take Shadowflame damage. Orbs of darkness then converge on the impact location, inflicting Shadowflame damage to any players in their path. Players that absorb these fireballs should quickly move to avoid the orbs. Other players should make note where the fireballs are landing so an orb does not spawn on them.
A major change in Mythic is that Corrupting Shadow and Blazing Heat are now permanent. If a player with Corrupting Shadow touches a player with Blazing Heat they trigger Volatile Shadowflame. This deals Shadowflame damage to players within 5yds of the eruption. All Corrupting Shadow or Blazing Heat stacks will be removed from both players, and they will gain stacks of Lingering Shadow or Lingering Flames equal to how many stacks they had of Corrupting Shadow or Blazing Heat. For example if a player had 5 stacks of Corrupting Shadow and cleared, they would gain 5 stacks of Lingering Shadow. Lingering Shadow deals shadow damage every second and increases the shadow damage the player takes by 10% per stack for 20 seconds. Lingering Heat does the same thing but with fire damage. The raid will need to manage clearing these dots throughout the fight. It may be beneficial for certain ranged DPS to purposely get both dots so that anyone can clear with them. The Eternal Blaze has a more minor change, its Swirling Flame will expel 5 fire tornados instead of 3.
The Shadowflame Amalgamation will cast Shadow and Flame throughout this phase. This will put Corrupting Shadow on half of the raid and Blazing Heat on the other half, and deal damage to any players within 6yds of each other. These effects are permanent and gain a stack every 5 seconds. Players will need to spread before the cast finishes to avoid the splash damage. Depending on the timing of other mechanics, it is probably best to clear the dots ASAP to keep their effects under control. Keep in mind players will still be gaining stacks of Shadowflame Contamination as the phase progresses so a lot of dot damage will be going out for healers to watch.
There are all the abilities you will see in the Amalgamation Chamber and how to deal with them.