Once a prized pupil of Magatha Grimtotem, this master of the primal elements is preparing to unleash his most devastating creations. If Kurog is not stopped, his entities of storm, fire, ice, and earth will wreak havoc across the whole of Azeroth.
This page is purely speculative based on the Dungeon Journal. It will be updated as tests go on.
Kurog Grimtotem is a three phase encounter.
Phase 1 you fight against Kurog, he will gain stacks of power from whichever altar he is nearest to.
I suspect this to be very similar to Lei Shen, where he gained abilities based on which altar area you had him in. Map illustrating this below.
At 66% & 33% Phase 2 will begin where Kurog will spawn two elementals and be shielded. When these elementals are defeated you return to Phase 1.
Simialr to the above, I suspect this to be the two highest empowered elements are selected.
Once all 4 elementals have been defeated Phase 3 begins where Kurog has the power of all 4 elements.
Elemental Surge - If Kurog is not near an altar he will apply a stacking DoT to the raid and gain a stack of every elemental type every second!
[Heroic/Mythic] 
Elemental Shift - Kurog will do a high of raid wide damage when he connects to an Altar. Additionally, this will debuff the raid for 40 seconds with Primal Break which increases the damage taken from Elemental Shift by 80% for 40 seconds.
This looks to prevent you from swapping between two altars and keeping Kurog in a constant spell queue state.
Sundering Strike - This is the tank swap of this encounter and presumably a 1 stack swap.
Kurog will deal a high amount of Physical damage to everyone in a cone in front of him. This will also apply a stack of a DoT which deals Physical damage for 35 seconds.
[Mythic Only] 
Primal Gains - When the Mythic only adds die he will gain all of their stacks, making killing adds a priority.
Magma Burst - This will target a maximum of 3 random players and apply a DoT to them. After 10 seconds this debuff will expire and create a 
Lava Pool.
Lava Pool - Standing in a Lava Pool will deal a very high amount of Fire damage every second.
[Heroic/Mythic] 
Molten Rupture - Waves of lava will fire at random players in a pattern. Any player hit will take a near lethal amount of Fire damage.
Unclear on what this pattern may be. Testing will show us. I suspect this to be some kind of pulsing ring collapsing on the player.
Searing Carnage - This will target a maximum of 3 random players and mark their location every second. After 1.5 seconds the 5 yard area will explode for a lethal amount of Fire damage.
The players will also have a DoT applied to them which deals a moderate amount of Fire damage every second for 5 seconds.
Each successful cast of Searing Carnage will give Kurog a stack of 
Blistering Dominance.
This type of mechanic will typically be dealt with by the raid stacking. People who get Searing Carnage run one way, everyone else runs the other way.
Blistering Dominance - Increases Kurogs Fire altar ability damage by 5% per stack.
Flamerought Eradicator - Mythic only add will write later. Offtank will be on it.
Biting Chill - Kurog buffs himself and deals raid wide damage every second for 10 seconds.
[Heroic/Mythic] 
Frigid Torrent - Sets of orbs will be thrown into the room every 2 seconds for 4 seconds. If you touch an orb you will take a large amount of Frost damage and be stunned for 6 seconds. This is dispellable.
I presume this to be a set of orbs at 0 seconds, 2 seconds and 4 seconds for 3 sets total.
Absolute Zero - This will target a maximum of 2 random players. After 3 seconds they will take a lethal amount of damage, this damage is split by everyone within 8 yards.
Any player hit by Absolute Zero will have a stack of 
Frost Bite applied.
If you receive multiple stacks of Frost Bite you will be 
Frozen Solid. This bypasses all immunities.
Each successful cast of Absolute Zero will give Kurog a stack of 
Chilling Dominance.
You are not able to stack as a raid to make this mechanic easier as if you are hit by multiple you are Frozen Solid.
Chilling Dominance - Increases Kurogs Frost altar ability damage by 5% per stack.
Icewrought Dominator - Mythic only add will write later. Offtank will be on it.
Erupting Bedrock - 5 second cast, anyone within 15 yards takes a lethal amount of damage and is knocked back.
[Heroic/Mythic] 
Enveloping Earth - A maximum of 3 players receive this debuff dealing a moderate amount of Nature damage and have a very large healing absorbtion shield applied to them.
Seismic Rupture - Areas of the room are highlighted and Earth Breakers will spawn from them. If you are stood in 10 yards of any of these areas you will take a lethal amount of Nature damage and be knocked back.
Earth Breakers will deal raid wide damage every 2 seconds and apply a stack of 
Skeletal Fractures which increases Physical damage taken by 6% for 10 seconds.
Each successful cast of Seismic Rupture will give Kurog a stack of 
Shattering Dominance.
It's not explictly stated that Earth Breakers are adds, but from looking at the data they appear to be Earth Elementals you need to kill quickly else your tanks are going to die from the stacking Physical damage taken debuff.
Shattering Dominance - Increases Kurogs Earth altar ability damage by 5% per stack.
Ironwrought Smasher - Mythic only add will write later. Offtank will be on it.
Shocking Burst - A maximum of 2 players will have this debuff applied to them. After 5 seconds the debuff will expire and deal a large amount of Nature damage to all players within 12 yards.
[Heroic/Mythic] 
Lightning Crash - A maximum of 3 targets will receive this debuff. After 4 seconds the debuff will expire and increase Nature damage taken by 70%. It will also deal a small amount of Nature damage to the closest target every second for 10 seconds.
Here you will likely need to segment the raid as people who have the debuff on the left and people without on the right so that you can easily ensure the person you are cleaving to will not take increased damage.
Thunder Strike - Areas of the room are highlight and Thunder will fall on it dealing a large amount of Nature damage to players standing within 8 yards of the location.
If any of the Thunder Strikes are not soaked by a player a lethal amount of raid wide damage will be dealt.
Each successful cast of Thunder Strikes will give Kurog a stack of 
Thundering Dominance.
You may need a rotation of players with defensive abilities to soak these. At the very least your offtank can solo one.
Thundering Dominance - Increases Kurogs Storm altar ability damage by 5% per stack.
Stormwrought Despoiler - Mythic only add will write later. Offtank will be on it.
At 66% & 33% Kurog will create elementals from the two most empowered alters (assumption).
Kurog will also have a 
Primal Barrier which reduces his damage taken by 99% in this phase.
Primal Gains - When an elemental dies all of the stacks it has will transfer to Kurog.
After all of the elementals have been defeated from Phase 2 the final Phase will begin.
In this Phase Kurog has all of his abilities from Phase 1, but cast them faster!
Unkown until testing, speculated numbers above.
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