Trial of the Crusader 1

And it's almost over. The fourth and fifth boss encounters are much more epic than the previous encounters, actually reaching the difficulty of some Ulduar bosses.
Boss Encounter 4: The Twin Val'kyr
Before the bosses enter, designate who will take the Dark Essence or Light Essence buff.
When you start the encounter, the Dark Val'kyr will move south and the Light Val'kyr will move north. They will stop close to the northwestern and southwestern points of the star design on the Coliseum's floor. The essences will be on the northwestern, southwestern, southeastern, and southwestern.
You will need two tanks for these bosses. If you're relying on a Paladin tank, have them tank the Dark Valkyr. Paladin tank skills will have very little effect on the Light Valkyr.
The tanks should pick the essence that is the same color as their target boss to reduce the amount of damage that they take. Classes with threat- Ulduar. Surge of Light and Surge of Darkness will deal raid-wide damage directing skills will need to use those skills for the duration of the encounter.
This fight is healing-intensive, comparable to Ignis the Furnace Master in every two seconds from the very start of the encounter. You can minimize the damage from one of the surges by picking an essence. The damage from the opposing element will increase, but the overall damage is lesser than not picking an essence at all.