Splits 2,300,000 to 2,700,000 damage between all targets within 25 yards. Morchok's current target and their closest ally will take a double portion of the damage.
Crush Armor
Reduces an enemy's armor by 10% for 20 sec. Effect stacks up to 10 times.
Resonating Crystal
Splits massive Shadow damage between the three closest enemies. The total damage increases the further the targets are from the explosion.
Furious
Decreases the time between your attacks by 30% and damage increased by 20% for until cancelled.
Black Blood of the Earth
Morchok channels an intense spell, causing fragments of his body to fall free and draw the blood of the Old Gods to the surface.
Strategy
This is a one phase fight that has a set of mechanics that need to be followed in a repeated sequence. Basically, if you can do it correctly once, you're set for the rest of the fight. We'll go over each ability that happens in the order that it appears.
The first thing the boss has is Crush Armor. This is an armor reduction debuff and requires two tanks. Each tank will take 3 stacks, then the other tank taunts. Rinse and repeat.
The next ability he has is Stomp, which happens about every 12 seconds (a total of 3 per "round"). This ability does 3 million damage split among everyone who gets hit by it. For example, if all 25 players get hit with it, then each person will take 120k physical damage. Therefore, it is important that everyone stacks up and is within 30 yards of the boss. There is one other important thing to note, the two closest players take double the damage so both tanks should always be closest to the boss, have melee stand at maximum hit range.
The next ability he has is Resonating Crystal. He'll spawn two of these at a time (in 25 man), and he'll do this twice per "round." Each crystal will target the 5 players closest to the crystal. After 12 seconds, the crystal will explode and do damage to these 5 players based on how far away they are from the crystal. Adding more players does not help, and it actually makes matters worse since additional players will take the full damage. Note that the base damage is 500k split among the 5 players, meaning the minimum damage is 100k per person. To handle the crystals, 5 players will need to stand on top of the crystal as quickly as possible to minimize the damage taken. Healers should make sure these 5 players are topped off before the explosion happens. Also, the explosion causes a knockback.
Pro Tip: ALWAYS TAKE A STOMP BEFORE RUNNING TO THE CRYSTAL!! Not being stacked for the stomp will likely wipe the raid.
After two sets of crystals, the boss will do a chain of abilities that everyone needs to take note of. First, he'll so Earthen Vortex. This will pull everyone on top of the boss and do 50% of each player's max health as damage. Just make sure everyone has more than 50% of their health when this happens. The key players that healers will need to be worried about are those who recently took a crystal.
Next, he will channel Falling Fragments. This will cause several fragments to spawn around the area. Once the fragments are on the ground, he'll cast Black Blood of the Earth. This will spawn a large black pool that spreads outwards. If you stand in this pool, you will get hit with Black Blood of the Earth, which will kill you very quickly if you don't get out fast enough. To get out, you must head for the fragments that spawned and line of sight yourself from the boss. Healers will need to top off anyone who got hit by the pools. This lasts for about 20 seconds.
After the boss is done channeling, the raid can move back to the boss. The fight repeats itself until the boss hits 20% health. At this point, the boss will become Furious, where he will attack faster and hit a bit harder. As long as the raid is topped off this should be a kill. Players should used defensive cooldowns and healthstones, and this is also the ideal time for bloodlust (if your healers are struggling).
Heroic Strategy
There are several key differences that make the heroic fight more difficult. First, at 90% health, the boss will create a twin called Kohcrom. Whatever ability the boss uses, Kohcrom will use the exact same ability 10 seconds later. This normally wouldn't be a problem. However, Stomp works differently in that it also applies a debuff where you take extra physical damage. In other words, if you get hit with a Stompwith the debuff, you're dead. The good news is that Crush Armordoesn't happen in heroic mode.
To handle the stomp issue, the raid will be divided into two teams: left and right. Each team will consist of 1 tank, 3 healers, and 8-9 DPS (8 on the left, and 9 on the right). Kohcrom's side is less damage so you can short healers if you are confident in keeping that team alive. Each team will also consist of a Rogue who can Feint every stomp to serve as the second person to get hit. With the nerf any other class can soak but it is important to consistently have one DPS soaking the stomps and using CDs for it. The stomp deals physical damage so use a proper CD.
Resonating Crystal now requires 7 people to soak instead of 5 so adjust assignments accordingly.
Once the raid is split into two teams, the fight becomes quite similar to normal mode. Be near the boss for the stomps, and DPS stand on top of the crystals when they spawn.
Pro Tip: Once each team has a good idea where the crystals will spawn, the team can position themselves around the boss so that they can move immediately to the crystal. This will minimize movement and maximize damage.
While the stomps and crystal spawns happen about 10 seconds apart from each boss, both will use Black Blood of the Earthat the same time. The raid simple hides behind the pillars, staying out of the black ooze on the ground. If positioned correctly, ranged DPS can continue to damage the bosses and avoid black blood damage. The fight then repeats itself.
Ast 20% health he will still use Furious. Bloodlust will need to be used at this point, and you need to be ready to use raid cooldowns for each major hit. As long as everyone is in the right spot at the right time, and the healers can keep the tanks up, he should go down.