As you enter the spire past the green jets of death, the first mobs you'll see flying around the central spire are the Val'kyr Heralds. The Heralds themselves aren't so bad to kill, but they have a trick that can send your groups into apoplexy. As the fight against each Herald proceeds, they will drop a Severed Essence on members of the raid. That ability creates a Severed Essence mob -- a duplicate of one of your raid members. The longer the fight against each Herald continues, the more Severed Essences you'll have to fight. It's probably best to have your off-tank pick up these additional mobs, while you focus on burning down the Herald. Then go back and clean up the Essences at your leisure. The jets and the val'kyr are not actually Plagueworks trash, but you'll have to deal with them on your way there.
Stinky and Precious
The next fight I really want to talk about is the showdown with Precious and Stinky. We'll go one by one, but to sum up: welcome to Gluth 2.0 and 3.0. Both Stinky and Precious sport a Decimate ability, so your healers will definitely need to be ready to handle that when it drops. Equally problematic for healing your tanks are the rapid-fire stacks of Mortal Wound that will slow down your healing on the main tank. Mortal Wound will stack up to ten times, at which point no healing will successfully land on your tank.
Let's start with Precious. The general heartbeat, so to speak, of the fight with Precious is very similar to the fight against Gluth. You'll need two tanks. When the stacks of Mortal Wounds gets too high to heal through, swap the mob between the two tanks. It's best to taunt to a fresh tank just after a Decimate drops, if you can at all arrange it that way. Precious also summons lots of zombies, but these zombies do not heal Precious when they reach Precious. I've found it best to kite Precious down the stairs and then back up the other stairs, so that the tank isn't carrying too many zombies all at once. The zombies walk pretty slow, so you won't have too much trouble.
Stinky has the same Mortal Wound and Decimate dynamic as Precious, but has no zombies. Instead, Stinky smells bad, and is constantly shooting out an aura of Plague Stench. Plague Stench will constantly deal raid damage to anyone in line of sight of the dog, so it's best to burn Stinky down as fast as possible. Think of this fight as a healer check, since it will definitely push your healers hard to keep the entire raid topped off.
Festergut is probably one of the two ugliest bosses in the game right now. The other would be Rotface, who shares the same model as his brother. The fight with Festergut is actually fairly straightforward, and only has two different gimmicks. The first is the Gastric Bloat he puts on the tank, which will require you to have multiple tanks. The second is the Gaseous Blight that fills the room when you enter. Here's how all this works out.
The first trick with Festergut is the stacking debuff called Gastric Bloat. This debuff will stack up to ten times on the tank. When it reaches ten stacks, the tank will explode in a funky Gastric Explosion. The explosion will hit your raid hard -- it instantly kills the person who exploded, and does huge damage to everyone else in the room. So, obviously, you don't want to let the Bloat go to ten stacks. Have your off-tank taunt Festergut when the first tank has 9 stacks of Gastric Bloat. It takes two minutes for the debuff to drop off, which is also how long it takes for the Bloat to get to 9 stacks in the first place. When a tank is "cooling down" their bloat, they should be DPSing the boss, since the Gastric Bloat also has the side effect of increasing the target's damage by 10% per stack.
Ranged DPS (and healers) will need to worry about Vile Gas, a debuff that encourages them to spread out at all costs. If you get too close to other players with Vile Gas, bad things will happen.
The other thing to worry about is the ongoing Gaseous Blight that fills Festergut's room. It starts off incredibly powerful, and will tax your healers to keep the raid at full health. Festergut will periodically "inhale" the gas, which makes him hit harder, but the Blight a little weaker. After he's inhaled four times he farts a Pungent Blight, damaging the entire raid. So, this is the ebb and flow of the fight: the raid is taking a lot of damage from the Gaseous Blight. With each inhale, the raid takes less damage, but the tank takes more. So your healing will slowly shift from raid-focused healing to tank-focused healing. When Festergut reaches four inhales, he will explode and kill everyone with a big Pungent Blight. However, there's something you can do to keep the raid from dying from that one, big fart.
Festergut will periodically drop a Gas Spore on random raid members. (It drops 2 spores in 10 man, but 3 spores in 25 man.) That spore will explode, doing light damage to any player within range and providing them with a Inoculated buff. That buff will keep you from taking deadly-level damage from Festergut's Pungent Blight fart, and becomes key in letting your healers successfully heal through the encounter. For that reason, it's a good idea to keep your melee in a clump, and make sure your ranged collapse for spores. However, once the spore has popped the range need to spread out again lest they murder each other. (Editor's Note: Edited the previous sentence for encounter clarity.) When the spores occur, have the spore-players be sure to spread out across the two groups.
Once you master these dynamics, you'll actually find Festergut fairly easy. He does have a 5 minute enrage timer, so you need to be certain you have enough DPS to get through the fight. If you find yourself short of the damage throughput to kill him within 5 minutes, you may need to adjust your strategy.
Good luck hunting out there, folks.
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