Cataclysm Guide: The Stonecore

Updated Wed, May 11, 2011 by Messiah

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NOTE: This guide has been updated to include all the information on the both the Normal and Heroic versions on the bosses.

Time to enter the Stonecore

The Stonecore instance is located in Deepholm, the earth elemental plane. The instance portal is located right in the center of the zone on a platform up the side of the pillar where you enter the zone, on the southeast side. Once you know its rough location it is extremely easy to find. This instance is meant for players level 82-84 and can be extremely challenging if you are on the low end of that scale.

Being based in an earth elemental zone it should be no surprise to players that the instance has a very rough rock hewn appearance. It looks like a cave carved out of a mountain, while still being open enough at points to show how large the space is. At times you are in tightly confined tunnels and at other times you are on ledges overlooking a vast expanse below. If anything the open space almost seems too big to be found in the space where it is located, but hey, it’s a game and it’s pretty, so we’ll let it slide.

A map of the Stonecore

The trash creatures (enemies in an instance that are not the boss) are varied and challenging, especially the first few groups. When you first enter the instance you will find Millhouse Manastorm, whom you should recognize from the past, helping out the first few groups against you.  These groups are a pretty tough check to see if you are ready for the instance.  They all do significant damage and need to be controlled until each one goes down.  In addition to the creatures you also need to deal with Millhouse, dropping his health low enough that he retreats to the next group of creatures. If you can get by the first few groups you should be ok until you get to the final boss, as these groups are almost more difficult than the first few bosses


Corborus is the first boss in the instance and appears as a giant elemental worm made up of rock rings as segments. He is a very cool looking boss especially since he matches the theme so well.

Corborus Abilities


Burrow – Corborus tunnels under the ground, releasing weak adds above him.  Also deals significant damage (20,000+) to anyone that does not move away from him.
Crystal Barrage– Sprays small crystal shards at a target and leaves them on the ground for a short while.  They deal damage over time to anyone that remains withing 5 yards of them.
Dampening Wave –This is a frontal cone attack that deals shadow damage and applies a debuff that absorbs 400 points of healing. The debuff stacks up to 20 stacks. Make sure Corborus is faced away from the group.

Corborus Strategy

The fight is not that difficult, as it is made up of two simple phases. In the first phase Corborus will be above the ground.  The tank simple needs to keep him faced away from the group. Anyone targeted by the Crystal Shards simply waits until the shards start flying at them and then moves out of them.  Anyone else in the area needs to move away as well.

After a certain amount of time Corborus will dig into the earth.  At this point you can only see where he is by watching the heaving ground.  It is imperative that everyone watch where he is and move out of his way.  Anyone caught above him will take significant damage and be thrown through the air and potentially too far from the group to be healed.  During this phase he will also spawn small adds continuously.  They are very weak and plays simply need to kill them before there are to many up at once.

After a while Corborus will get bored playing in the mud and surface to deal with you once again.  This returns the fight to phase one.  Defeat him and move on.

Corborus Heroic Mode

There are a few differences with the Corborus fight that make a big difference when done in Heroic mode. This is of course in addition to the much higher health and more base damage caused by all heroic bosses.

The first real difference is that the Crystal Barrage does significantly more damage and has a secondary effect. Once landed the crystals will float up and towards a random player, if they hit that player they explode for upwards of 40,000 damage. They need to be AOE'ed down as quickly as possible.

Secondly, when Corborus is burrowed underground he does more damage to the group and can leap in the air. If he lands on you the damage caused will kill you, so keep moving. To allow a little more time for players to avoid Corborus's burrow phase, the tank should hold him significantly farther away from the group than in normal mode.

Lastly, the adds that surface while Corborus is underground have much more health, cause more damage, and apply a bleed debuff. Killing them fast is critical, they are not a joke like they are in normal mode.


Slabhide is an undead looking dragon that you must defeat.  Expect the normal dragon abilities, meaning stay away from his front arc and away from his tail.  He of course has other abilities as well, but whenever you’re fighting a dragon it’s a good idea to keep those basics in mind.

Slabhide Abilities


Ceiling Collapse – While Slabhide is in the air he can knock down stalactites from the ceiling.  A shadow will appear to show where the stalactite is going to drop.  If you are there when hit hits the ground you will take a lot of damage.
Sand Breath –
This breath attack hits everyone in Slabhide’s front arc and within 20 yards for significant damage.
Eruption– Slabhide targets an area that explodes causing fire damage to anyone on the marked spot. Also a pool of lava will be left behing that lasts for roughly 10 seconds causeing fire damage to anyone silly enough to stand in it.

Slabhide Strategy

The fight is fairly simple fight that is split into two phases.  In the first phase when you first engage Slabhide the tank simply needs to face him away from the rest of the party and hold him there.  The group needs to DPS Slabhide while avoiding any magma bursts that are thrown their way.

After a period of time Slabhide will disengage and fly into the air.  While in the air he will tear stalactites off of the ceiling to fall down onto players.  There will be a shadow that shows up to show where it will land.  Simply move out of the shadow to avoid the damage.  You have roughly 3 seconds which is a lot of time to avoid the damage.

Once he lands the tank simply picks him back up and faces him away again.  This restarts the first phase.  Repeat as required until you have defeated him. Keep in mind though that there can be a large number of stalactites and they do block line of sight, so check your LOS to your healer often.

Slabhide Heroic Mode

Slabhide is a difficult fight for many groups on normal mode due to the LOS issues caused by the stalactites, and it gets even worse in heroic mode. This is due to more damage being caused that needs to be healed and an additional ability that he gains in heroic mode.

The ability is called Crystal Storm and is cast at some point after Stalactites have fallen. The group is given some warning that he is about to cast and then he spays out crystals in all directions and anyone that is in LOS of him is hit for roughly 20,000 damage per second for 6 seconds. The only way to avoid the damage is to find cover behind a stalactite. This however will block all incoming heals as well while you hide.

Once the Crystal Storm is over, the fight reverts back to the ground phase.

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