Two realms that coexist on top of each other. You can right click the Spirit Fonts on the side of the room to go to the other realm. We will pick 2 healers, 4 dps and a tank to go into the spirit realm.
INSIDE SPIRIT REALM:
Wailing Souls will be on a lengthy timer and it is a 1 minute long channel that will deal moderate Damage to everyone in the Spirit Realm.
ALL ABOUT THE ADDS!
Soul Residue adds will have highest priority. They spew green shit on the ground that will deal damage. If you have one targeting you, move to the edge of the room, to leave room for people to run around. Ranged should kill them because they will explode and deal damage to anyone within 5 yards and knock them back when they die. (These adds can be stunned, slowed, gripped or displaced.)
Fallen Priestess: Will apply a debuff that will deal some shadow damage and prevent targets from crossing realms, as well as slowing move speed. This can be dispelled as soon as possible.
They will cast Shattering Scream, which is interruptible, that will give a random player a stacking debuff that when it reaches 5 stacks, that person will explode and take moderate damage and remove Bonecage Armor from the adds in the Corporeal Realm. (If you get Shattering Scream, you will go to the area we will have marked in the spirit realm).

OUTSIDE SPIRIT REALM:
Engine of Souls will need to be tanked in this realm. He will throw out a Bone Shards ability which will need active mitigation.
Collapsing Fissures will spawn on random players throughout this realm and leave a zone that will slow move speed and you will take moderate damage if you stand in them. Those zones will last 1.5 minutes, so when that ability is about to come out, make sure to be on the edges of the room.

Soulbind will bind two targets from opposing realms together who will deal shadow damage to everyone around them until they are within 5 yards of their bound buddy. We will mark a spot in each realm to go to if you are bound.

Tormented Cries - You will want to get to the edge of the room, along the sides. When it goes off it will leave a line of purple stuff that will silence and deal damage to everyone within the line. This line will show up in both realms.

Reanimated Templar will be there at the start of the encounter. You will want to avoid the shockwaves he will put out. When he reaches 50% he will gain 95% Damage Reduction that can only be removed by the Shattering Scream explosion from someone in the spirit realm.
Two Bonewarden adds will also be there at the start of the encounter, and will receive the same debuff once they hit 50%, so you want all the adds to be around the same health so they can all have the debuff removed from them at the same time with the Shattering Scream.

Before 30% on the Engine of Souls, you need to make sure all the adds are dead so you can focus the Desolate Host, which is what the Engine turns into at 30%.

The Desolate Hosts main ability is called Torment, which is a stacking debuff where he gains increased damage over time. Sundering Doom will be different for each realm. Those in the Spirit Realm will want to get away from the boss and those in the Corporeal Realm will need to be grouped up in the bosses circle.
Doomed Sundering is the opposite. Those in the Spirit realm will group on the boss and those out of the spirit realm will run away to avoid lethal damage.

Lust usually at 30% when the Desolate Host spawns. Battle Rezzes cannot cross realms, same thing with Bloodlust. So you will want at least 2 people with Battle Rezzes in each group.