How to: Grobbulus for Dummies guide (3,000,000 Hit Points normal/ 9,600,000 Hit Points heroic).

Grobbulus is maybe one of the most hated encounters in Naxx, because it requires a lot environmental awareness from all members of the raid. A single unalert member can cause a wipe, and if that repeats the encounter might get frustrating.
Therefore it is very important that all raid members understand the way this fight should go.

Grabbulus Abilities overview:

•    Poison cloud (15 seconds CD):

Grobbulus drops a stationary AOE gas cloud where he stand, that will remain there (and expand in size) for 75 seconds before fading. The gasses will cause a very high DoT to anyone inside (2K per second in normal and about 4K second in Heroic).

This Ability will keep the tank moving to avoid the clouds himself.

•    Slime Spray

Grobbulus will spray this on targets in from of him. This will cause heavy damage on impact (about 11K on heroic) to the raid member, and summon Slimes at the point of impact as well.

Tanks and raid should then make sure Grobbulus NEVER faces the raid, or it will turn to a nightmare version of "Gremlin" and the raid will wipe.

The slimes do a nasty AoE damage (1-2 K per second) on heroic, so they should be picked by Off Tanked and downed ASAP.

•    Mutating Injection (20 seconds CD)

This is the ability that makes this encounter so highly demanding of the raids members self awareness.

Players that get injected by this ability will get a debuf that after 10 seconds (if not cleaned, and it should NOT be cleansed) will do mediocre damage to them and will place yet a new gas cloud at their feet, just like the Poison Cloud ability.

Because this has the potential to fill the room with tons of cloud gas that may trap the Tanks path and make a huge AOE damage in the middle of the raid, the tank should leave gaps in the "gas cloud tail" where injected players should run and wait for the injection to "go off".

Healers cleansing these clouds too soon will make the cloud go off too soon in inconvenient places, therefore cleansing should not occur in this fight.

The following strategy will be needed to avoid a scenario where the room is filled with tons of gas clouds that trap the tank and /or cause overwhelming AOE damage to the raid (Below are pictures of a bad Gas locations that trap the tank, and one of a good Gas Location. Green Clowd = Cloud dropped by Grabbulus, pink Clowds= released by injected players).

Naxx Bosses "For Dummies" Guides:

Naxx strategy FAQ Guide

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Grand Widow Faerlina strategy

Maexxna strategy

Noth the Plaguebringer strategy

Heigan the Unclean strategy

Loatheb strategy

Instructor-razuvious strategy

Gothik strategy

Four Horsemen strategy

Patchwerk strategy

Grobbulus strategy

Gluth strategy

Thaddius strategy

Shappiron strategy

Kel'Thuzad strategy

Related Links:

* Ultimate Complete WOW Guide

A: Bad Gas Locations
Tank is trapped.
bad gas locations on Gabbulus fight

B: Good Gas Locations
Gas spots out of the way.

Grobbulus strategy:

1.    The tank pulls Grobbulus near the stairs, and makes sure he's not facing the raid.
2.    The tank starts "Kite tanking" Grobbulus along the wall lines, in a way that leaves "gaps" between the gas clouds
3.    If players are hit by Slime Spray and Slimes spawn they are picked up by OT and Killed First Priority.
4.    Whenever a player gets injected he runs to the gaps between the gas clouds, and wait for the injection to "go off", then runs back to the raid.
Again: NO ONE CLEANSES THE INJECTIONS.
5.    Continue this method as much as needed until Grobbulus is down.

Differences between 10 and 25 man version:

There aren't any. Assume in the first few rounds (will DPS increases and he's killed faster) to do a full round around the room, so raid members have to be very disciplined and follow the described strategy.

Tips and Notes

• You will have 12 minutes in Heroic and 9 on Normal to down him, which is a lot of time.

DPS should be relaxed about the damage meters and give first priority to being aware to their environment, and most importantly, whether they are injected or not.

• After Grobbulus dies wait for cloud to fade before looting. Looting too early might make you die to Gass clouds, and put the mark of shame on your character for all eternity.

Good Luck!