Originally Posted by AlienaHello and welcome to the TankSpot Bastion of Twilight Raid Guide! My name is Aliena, and in this video I'll show you all you have to know about Cho'gall, the fourth encounter in this new raid instance. We completed this fight with 2 tanks, 3 healers and 5 DPS, but similar raid configurations may work just as well.
10-man Cho'gall has 33.5 million health and is a two-phase encounter. While he has an intimidating number of abilities, the fight is actually fairly straightforward. The entire fight is based around a Corrupted Blood Mechanic that works similarly to Atramedes' sound bar. At the start of the fight, a Corrupted Blood meter will pop up in your UI, and getting hit by any of Cho'gall's or his minions' abilities will increase your corruption.
Depending on how much Corrupted Blood you accumulate, different things will happen. At 25 stacks, you get a magic debuff that greatly accellerates your stack gain. This can and needs to be dispelled. At 50 stacks, you periodically get a debuff called Sickness, that'll make you vomit onto any raid member in a 5 yard cone in front of you. At 75 stacks, you grow a tentacle that will cast Shadow Bolts at your raid members. At 100 stacks, you're immune to any healing but will deal 100% more damage.
The goal in the normal encounter is to keep your stacks as low as possible throughout the whole fight. When you trigger phase 2 at 25%, Cho'gall will activate a spell called "Corruption of the Old God", which deals shadow damage to every raid member every 2 seconds until he dies. This spell will deal more damage the more stacks of Corrupted Blood you have, and each tick of it will cause you to gain 1 stack of Corrupted Blood.
As you can see, phase 1 is all about keeping the fight controlled and avoiding as many of Cho'galls abilities as possible, whereas phase 2 is a burn phase, a race against Corrupted Blood stacks.
Let's go over Cho'gall's phase 1 abilities. As soon as you engage him, he'll switch into a stance called Flame's Orders. Cho'gall will switch between this stance and another stance called Shadow's Orders throughout the entire phase 1. While in Flame's Orders, Cho'gall's melee hits will deal an extra 20,000 damage and he'll spawn little fire puddles all over the room. Fire is bad news, don't bathe in it. Make sure your Cho'gall tank receives a lot of healing during Flame's Orders.
Shadow's Orders will cause Cho'gall to omit 3 pulses of a Shadow AoE spell. This seems to hit harder the more stacks of Corruption people accumulate and your healers need to be prepared for it. He'll switch stances approximately every 20 seconds.
The reason you need two tanks for this fight is Fury of Cho'gall - this is cast on his main threat target, deals 60k damage and greatly increases shadow and physical damage taken for 45 seconds, so when a tank is afflicted by Fury, the other tank should taunt off of him fairly quickly to minimize the chances of tank deaths.
The next ability you need to watch out for is Worship - this will mind control 2 random raid members. Worship can be interrupted by any stun, scatter, silence or fear effect and the sooner you do so, the better. While your raid members are mind controlled, Cho'gall will stack up a damage buff called Twisted Devotion. Each stack gives him 10% increased damage, and this stacks up to 20. To counter this, we had everyone stack up on Cho'gall for most of the phase, so everyone could be interrupted quickly by abilities such as Shockwave, Scatter Shot, Psychic Scream and many more.
The only exception to the stacking up is whenever Cho'gall summons a Corrupting Adherant. This happens approximately once per minute, and as soon as the add spawns, your raid should spread out to avoid getting hit by the add's Corrupting Crash ability. Corrupting Crash looks like a little shadowy swirl on the ground, and a few seconds after the swirl appears, a missile will hit its center. If anyone is still in it by the time the missile hits, they'll take damage and increase their corruption stacks by 10.
Make sure that all your DPS switch over to kill an Adherant as soon as a tank has it secured. If you're the tank, make sure to face adherants away from your raid members. If you play a class with an interrupt, make sure to interrupt their Depravity ability, which is a raid wide shadow AoE with a 1.5second cast time. The adds NEED to be killed as soon as possible. If an add is still up by the time Cho'gall casts Fester Blood - which happens 40 seconds after an Adherant spawns - the add will gain a Shadow AoE ability that will pretty much wipe your raid.
Of course, those aren't the only gimmicks the Adherants have. Upon their death, they'll spawn a black puddle on the ground that won't disappear until you hit phase 2. Standing in a puddle will deal damage and increase your Corruption, but even worse is that everytime Cho'gall casts Fester Blood, 5 little slimes will spawn from each black puddle. Yes, each. That means if you've killed 4 adherants, you will have 20 slimes coming to eat your brains.
Of course, getting hit by the slimes will increase your Corruption too, so you want to avoid that. We dealt with this by killing all Adherants next to each other at the entrance to the room, so the slimes would all spawn in the same general area and had to travel a long way to get to us. Applying a frost trap or slowing them down through other means is also almost essential. On the first two slime spawns your ranged DPS will likely be able to take the slimes down by themselves, but on later waves melee DPS might have to help them out with Fan of Knives spam or other AoE abilities.
Controlling adherants and slimes is key to this phase, and if you manage to take them all down in a timely manner and without increasing corruption stacks by much, you're well on your way to defeating this encounter.
When Cho'gall's health hits 25%, you'll trigger phase 2. Any bloodlust or time warp effect should be saved for this phase. He loses most of his old abilities but he does retain Fury of Cho'gall, so your tanks need to keep taunting off of each other whenever that happens.
As mentioned before, he'll activate Corruption of the Old God, which will increase your Corruption stacks by 1 every 2 seconds and deal increasing damage. This is unavoidable, and each raid member needs to keep a close eye on their stacks. Any raid member hitting 25 stacks NEEDS to be dispelled as soon as possible, and any raid member closing in on 50 stacks needs to face away from anyone else to avoid vomitting on them.
Of course, since you'll take increasing shadow damage, this also acts as a soft enrage timer. Eventually, your healers just won't be able to keep up. Additionally, as soon as you hit phase 2 and every 30 seconds afterward, Cho'gall will summon 4 tentacles called Darkened Creations. These will channel a beam on random targets that reduces damage and healing done by 75%, deals damage and increases Corruption, so they need to be killed immediately.
To quickly wipe them out, designate a DPS leader and have all other DPS assist him on his target. When the tentacles are down, DPS can attack Cho'gall again. This cycle will repeat until Cho'gall dies. Make sure that no one vomits on any raid member, and if you have sufficient DPS and healing and keep controlling the fight, Cho'gall should go down. I've attached footage of the whole encounter in case you'd like to see how we dealt with the various mechanics in detail. Good luck and have fun!