Trial of the Crusader 2

Sphere Collection
As you go through the fight, light and dark spheres will appear at the edges of the arena. This happens before one of the Valkyr Twins casts a spell. Everyone in the raid should collect spheres that match their essence. They will take a little damage, but nothing compared to taking a sphere of the opposing element. If the bosses collect these spheres, it will add to their empowerment and once they've reached a certain number, will soft-enrage and deal considerable damage to the tanks for 15 seconds.
A popular tactic is to assign all ranged DPS to one essence and melee DPS with one healer to the other essence.
Ranged DPS should clump to the point that your character models overlap. During the sphere phase, the healer assigned to the melee DPS should filter any of the spheres that don't match the ranged DPS' essence. Melee DPS should do the same but to protect the tank in charge of their target boss. Ranged DPS will take in any matching spheres that are within 5-10 yards of their assigned position.
Once a player reaches 100 stacks of "Powering Up", they will gain Empowering Light or Empowering Darkness, increasing damage dealt. Any threat-direction skills that they have should be used on the tanks before the massive surge of damage pulls the boss from the tank.