The Amalgamation Chamber
The Amalgamation Chamber

Raid Boss

The Amalgamation Chamber

The eternal sea of ​​fire burns as hot as a thousand suns, while the essence of shadows blooms with darkness incarnate. Both are enormously powerful on their own, but when they are combined, the uncontrolled power of the Shadow Flame surges within them, creating a whirlpool of total destruction.

Heroic Changes
If the 2 Elementals are not at least 25yd apart, they deal 200% more damage. Keep them separated.
Casters can stand between them to cleave but would stack both DoTs, so make sure your healers can handle it. If not, simply play the swap. Melees should start on Fire Elemental and swap if needed.
In P1, the Shadow Elemental gains a new ability about dodging projectiles. The Fire Elemental gains a new ability about soaking projectiles.
In P2, the Shadowflame Amalgamation gains a mix of the previous abilities. You must soak some projectiles AND dodge others.
Mythic Changes
In P1 and P2, the Fire and Shadow Elemental DoTs are permanent and are cleared by having players with different ones collide.
The collision causes a small explosion at its location and players get a new Mythic DoT proportionate to the number of stacks cleared.
Assign each player a partner with whom they will regularly clear their DoT away from others.
When P2 starts, all players have their Fire and Shadow DoTs cleared, triggering explosions and applying Mythic DoT(s). If you never cleared your DoT(s) during P1, this will kill you.
In P2, the boss regularly applies the P1 Fire DoT and Shadow DoT to several players. Clear them just like in P1.

Corrupting Shadow - Blazing Heat

https://www.wowhead.com/en/spell=401809 - Players within 50yd of the Fire Elemental stack a 20s Fire DoT.Players within 50yd of the Shadow Elemental stack a 20s Shadow DoT that reduces their max HP.On Normal, tank both Elementals together; they should drop to 50% HP before the accumulation of both DoTs becomes dangerous.
tank both elementals together. the raid takes more damage as p1 goes on.