Ra-den the Despoiled
This is a two phase encounter. Phase 1 will change based on which orb is absorbed by Ra-den, and Phase 2 will begin when Ra-den reaches 40% Health.
Phase 1 (100-40%)
Nullifying Strike - At 100 energy Ra-den will cast this on the active tank. This will deal a large amount of Shadow damage and decrease your maximum health by 25% for 25 seconds.
Every ~55 seconds Ra-den will spawn a Vita + Void Portal at set locations in the room (as noted on the map above). An Essence of Void and Essence of Vita will spawn and move towards the boss. If you kill one of the Essences Ra-den will absorb the other, if any Essence reaches Ra-den he will absorb the essence.
Ra-den will gain abilities for 40 seconds based on the Essence(s) absorbed.
If Ra-den gets 2 stacks of the buff he will gain Overwhelming Rage, increasing his damage dealt by 300%.
Unleashed Void - Upon absorbing the essence everybody in the raid will have an absorb shield placed on them which deals a small amount of Shadow damage every 3 seconds for 40 seconds (or until healed off).
Unstable Void - A void missile will be launched from Ra-den to a location nearby. This will deal a large amount of Shadow damage to all players inside and will bounce in the direction the player was facing.
Please note: If multiple stand in this, it will not split the damage, but both players will get the Instability Exposure debuff. From testing I only had one person soak, so if multiple people soak it i would assume that the first person that entered will have the bounce go in their direction.
Phase 2 (40% - 0%)
Ruin - Ra-den will pulse a moderate amount of Plague damage to all raid members every 2 seconds.
Decaying Wound - This debuff will deal 100% of your current health at the time the debuff was applied, which will deal damage every 2 seconds for 10 seconds. Ideally you want to not use defensives for the Decaying Strike so the Decaying Wound is small.
Void Eruption - All targets within 12 yards of this will take a large amount of Shadow damage.
Note: If any adds are alive from Phase 1, they will also be buffed.
An additional portal is present on Mythic, the Nightmare Portal which will spawn an Essence of Nightmare.
Unstable Nightmare - A player in the raid will receive this debuff which will deal a large amount of Shadow damage to all players within 15 yards, after 6 seconds it will transfer to the closest player. This debuff starts with 5 stacks and a stack is removed for each transfer.
The duration of Unclaimed buffs (Unclaimed Void, Unclaimed Vita, Unclaimed Nightmare) has increased to 2.8 minutes (2 minutes 48 seconds) up from 1.3 minutes. This will mean that the orb you kill will need to alternate between all 3 orbs available.
Note: On PTR it would refresh the Unstable buff rather than stack to 2.
Chain Lightning - The cast from the Crackling Stalker will now increase in damage with each bounce.
Corrupted Existence - 3 players in the raid will take a large amount of Shadow damage and receive this debuff for 30 seconds. If they ever reach full health whilst having the debuff, they will die.
Tank Damage Profile
Position the boss to help your group kill the Essences (you may need to kite the boss from time to time)
During Phase 1, simply swap on each stack of Nullifying Strike
The tank who is not actively tanking the boss should be ready to collect the add(s) from the portal
Avoid collecting your Gift of the Ox orbs before Decaying Strike as the Decaying Wound will deal damage based on your health at time of application. (You may even need to cancel Ironskin Brew as the damage the Decaying Strike deals is hilariously low)
Vengeance Demon Hunter
Rallying Cry will be useful for the increasing amounts of damage the raid will be taking in Phase 2
Stampeding Roar can be useful to help your melee DPS get to an Essence
Blood Death Knight
If a Decaying Strike does go through and you have nothing to negate it, avoid casting Death Strike prior to the cast and heal up afterwards, as the Decaying Wound will deal damage based on your health at time of application