NOTE: This guide has been updated to have all the information on the differences between the normal and heroic versions for the bosses.

The Blackrock Caverns are one of two instances available to you when you first enter Cataclysm, the other being Throne of Tides. Blackrock Caverns is of course located in Blackrock Mountain which rests between the zones of the Burning Steppes and the Searing Gorge. 

In the mountain itself you can find the entrance by going around the east side of the walkway inside and going into the passage there.  This is the same passage you would use to enter Lower Blackrock Spire, but instead of continuing straight into the spire, you want to take the first right and enter the Caverns there.

The instance has a very similar look to both Lower and Upper Blackrock Spire.  As such you should expect to see lots of rock and fire.  Some players have complained it's a bland looking instance. However the whole place has a coherent look to the rest of Blackrock, and looks like a dungeon or cavern should, what else would it look like?  If you want colourful go visit the Throne of Tides, but if you want a no-nonsense old fashion dungeon, then visit Blackrock Caverns.

The trash creatures (enemies in an instance that are not the boss) are varied and challenging.  You will find a great deal of varied Twilight Hammer minions in the zone, including fire mages and ogres. The trash can be challenging for a new group that is fresh at 80 without raid gear from Wrath of the Lich King, but is manageable. In particular the Evolved Dracanoids that players may remember from other Blackrock instances and raids, are very tough and take a while to defeat.  Make sure you pull them separately and not with a group or you may be in serious trouble.

Rom’ogg Bonecrusher

Rom'ogg is a great boss to warm you up for the instance

Rom’ogg is the first boss in the instance and as such is a warm up fight.  While he is capable of doing a lot of damage if players do something wrong, the fight is not that complicated.

Abilities

Quake – Rom’ogg slams the ground creating an earthquake type effect around him.  It deals damage to anyone nearby for the next 3 seconds.
Chains of Woe – This spell brings everyone in towards Rom’ogg and places them in magical chains.  The group needs to break out of them before he uses his next ability.
Skullcracker –This attack is always cast right after Chains of Woe and takes roughly 8 seconds to cast.  When finished it will hit everyone in melee range for up to 100,000 damage. 
Wounding Strikes – This attack does slightly more damage than his normal attacks and leaves the target wounded.  The wounds reduce healing received by 25% for the next 6 seconds.

Strategy

The fight is pretty straight forward and is comprised of only a single phase.  Engage Rom’ogg and as soon as he casts quake players need to move out slightly.  When he casts Chains of Woe and everyone gets pulled in, simply defeat the chains while he is casting Skullcraker and then get away.  This includes the tank, as while most tanks with mitigation can take the hit, you will be left with almost no health and if the healer is delayed for any reason you will die.

If your group is mainly melee the quakes can cause issues if they do not clear out, but other than that the fight is simple for most groups.  He has a significant amount of health though so expect to take a while defeating him, which leaves more opportunity for someone to forget to clear out.

Rom’ogg Bonecrusher Heroic Mode

Rom’ogg when done in heroic mode hits much harder and a few modified abilities that needs to be watched for. When he casts his ability called quake, in addition to AOE damage around him it also spawns clouds of dust under each party member as the earth trembles. As soon as these appear players must move out of them as they inflict damage over time. Also once the clouds fully appear each will spawn an earth elemental type add that the tank needs to pick up and the group needs to AOE down. They have relatively low health so will go down quickly.

The rest of the fight functions the same as in normal mode with the exception that skull cracker which is cast right after chains of woe, will instant kill anyone in melee range. The chains only have ab lout 50,000 health though and you have 8 seconds to kill them and clear melee range, so as long as DPS switches to the chains immediately you should not have any issues.

Corla, Herald of Twilight

Corla requires some carefull add and debuff management

Corla is an interesting fight as you must deal with the main boss as well as two Evolved Twilight Zealots. While Corla herself is not much in the way of a fight, dealing with the Zealots is the real issue.  When the fight starts they are harmless, but don’t stay that way for long.

Corla’s Abilities

Aura of Acceleration – All friendly models near Corla increase movement speed by 50% and attack speed by 100%.
Dark Command – This spell causes the target to flee in terror for 4 seconds, while suffering shadow damage as well.

Evolved Twilight Zealots

Blood of the Evolved – This is a stacking debuff that causes Bleed effects to do additional damage.
Force Blast – This attack does damage as well as knocking you down.
Gravity Strike – Hits the target for 70% of their current health and places a debuff on them that lowers attack power by 1000.
Grievous Whirl – This attack hits for initial damage and places a bleed on the target.  The bleed will stay in effect until the player is healed to full health.
Shadow Strike – Steps into the shadows and appears behind their target, dealing up to 35,000 shadow damage.

Strategy

When the fight starts there will be Corla in the center and three Zealots kneeling before her.  A beam of energy will be coming from the back of the room to each of the Zealots.  The beam places a stacking buff/debuff on them.  If or when this buff gets to 100 stacks the Zealot will transform into and Evolved Twilight Zealot, until that point they do not participate in the fight.

The trick to this fight is not letting at least two of them transform at all.  This can be done by having players take turns blocking the beams coming to the Zealots by standing in the way.  When a player does this though, they will start gaining the debuff.  If they allow it to reach 100 stacks, and it stacks quickly, they will be mind controlled and granted additional power.  If a player is mind controlled, the fight is generally a wipe.

Therefore, as soon as a player blocking a beam hits 80 stacks they need to step out of the beam and wait for the debuff to clear.  During this time another player can step in, or just let it stack on the Zealot.   Some groups purposefully allow one Zealot to transform, so that there are two players to rotate through each of the other beams.  This is a safe strategy, however if you are fast on the beams, you can have one on each of the zealots and not have to worry at all.

Managing the Zealot transformation is the real issue in the fight, and as long as you can, Corla herself should not give you any issues.

Corla, Herald of Twilight Heroic Mode

Corla is not that much different in heroic mode, the main difference being that there are three adds to deal with and that the debuff lasts longer from the beam than in normal mode. The debuff lasts about 20 seconds and it takes about 30 seconds for the beam to charge someone to 100 debuffs. This means that one person can still deal with one add, they just need to be extremely careful on timing.

As long as you control the beams and do not allow any of the Zealots to transform the fight is very simple. A good strategy is to have the tank take the boss and handle the middle beam, and one DPS take each side beam, with the healer and other DPS as backup in case the timing for anyone becomes an issue.

Karsh Steelbender

He has some pretty tough armour on

The next boss is a nice change after the previous one’s complexity.  Karsh is a large Drakanoid that deals significant fire damage but does not have a very complex strategy.

Abilities

Obsidian Armor – This is a buff that reduces all incoming damage by 99%.
Superheated Obsidian Armor – This debuff is applied when the Obsidian Armor is heated.  For each stack Karash takes additional damage, but gains the following benefits:
Burning Metal – Deals additional damage to his target for each stack of superheated armor that he has.
Heat Wave – Deals 1000 fire damage to everyone nearby for each stack of superheated armor that he has.

Strategy

At the start of this fight players will quickly notice that Karsh is very hard to hurt due to his 99% damage reduction.  This introduces the main fight mechanic.

In the center of the room is a pillar of fire that the tank must drag Karsh into.  While there the tank and Karsh will suffer damage and Karsh will stack the debuff Superheated Obsidian Armor. The tank can position Karsh in the fire while he remains out with practice.

As the stacks build on Karsh, players will be able to inflict additional damage to him. However, he will also be doing additional damage due to a granted AoE fire effect from his heater armour, and doing additional damage to the tank.  Therefore the tank needs to manage the number of debuffs that Karsh gets.  Most groups seem to be able to deal with 4-7 debuffs at any given time.  This really depends on your healer and their gear though, so find what works for your group.

Whenever the debuffs on Karsh exipire, simply drag him back into the fire to reheat him.

Karsh Steelbender Heroic Mode

Karsh remains much the same as in normal mode, only doing much more damage. The only real addition is that as his armour cools to zero stacks of the heat debuff, adds will spawn around the room. These adds can cause a lot of damage, so need to be picked up, tanked, and killed before the tank drags Karsh through the fire to reheat the armour. This makes the fight last longer than in normal mode as there will be times you need to focus on the adds and leave Karsh alone.

Because this happens each time his armour cools, you will need to find the sweep spot for stacking the armour debuffs on Karsh. To many and he will do to much damage for your healer to keep up, too few and you will spend too much time dealing with adds in between heat cycles. Most groups find between 8 and 12 stacks to be the right number depending on your healer and tanks gear.

Beauty

Yet another Core Hound to put down

For players that started when WoW was released they probably remember the Beast in upper Blackrock Spire.  It is speculated that Beauty is the Beast’s mate, and in this instance you need to deal with her and her brood. No matter if she is related or not, she is a core hound and must die. Oh, did I mention her puppies?  Yes, you have to kill puppies too… sigh.

Abilities

Berserk Charge – Charges a random enemy, hitting for significant physical damage and throwing them back.
Flame Breath – She breathes fire and hits anyone in her front arc with it.
Magma Spilt – This attack targets a random party member and sets them on fire.  It deals initial damage and places a DoT component on them. Also, plumes of fire come up around the player that is infected.
Terrifying Roar – As with most core hounds, Beauty can send everyone away in fear.

Strategy

There are four puppies near Beauty and at least right now you can pull them and deal with them first.  However, it is wildly speculated that they are meant to be dealt with at the same time as Beauty and that the fight will be altered accordingly. 

For now, you simply pull and kill them before fighting her.  They have fire breath attacks to the front and drop fire zones that must be avoided.

The fight with Beauty at this time is pretty simple, with the tank simply facing her away from the group and beating her down.  When someone gets the fire debuff you just move away from the group, and return once it has been removed. It is because of this simplicity that it is believed the puppies should not be able to be pulled separately.

Beauty Heroic Mode

The Beauty fight is not very much different than in normal mode for the fight mechanics. The only two real differences are that her fear is more powerful (having a huge AOE and is cast very often) and when you pull her or one of the puppies you get all of them as a group.

Luckily the puppies are able to be CC'ed and if you have several CC capable players in the group they are easy to control. Just CC the puppies or kill them off, other than Runty, and then work on Beauty. Do not kill Runty or Beauty will enrage and wipe the group fairly easily.

Ascendant Lord Obsidius

He wouldn't be that bad if he would just hold still for a few minutes

The final boss in the instance is Ascendant Lord Obsidius.  He is an earthen and looks very much like a dwarf formed out of rock. In addition to fighting Obsidius, you must deal with two adds that place a healing debuff on anything they hit.

Abilities

Stone Blow– This attack hits for damage and knocks the player down.
Thunderclap – Hits everyone nearby for nature damage and slows them down.
Corruption – This is a shadow based DoT that lasts for 12 seconds dealing significant damage.
Transformation – Obsidius switches position with one of the adds.

Strategy

This fight brings back a long forgotten skill called kiting. Hurray for it’s return!  Basically how this fight works is that the two adds put a healing debuff on whatever they hit, reducing all incoming healing on that target.  For obvious reasons then, you can not allow the tank to be hit.  This means someone else needs to kite the two adds around the room while the boss fight is going on.

The adds are affected by most slowing effects, but immune to most stuns or complete stops.  The best class to kite them is a Hunter although other classes do work, such as Shamans and Mages for example.

While one player is dealing with the adds, the rest of the group deals with the boss, inflicting as much damage as possible.  After a short period of time Obsidius will swap places with one of the adds and reset everyone’s threat.  This is the key moment in the fight, because the tank must re-grab Obsidius, and the kiting players must re-grab the adds and separate them. Learning to control these switches is the hardest part of the fight.

Ascendant Lord Obsidius Heroic Mode

The final boss in heroic mode requires much more coordination than in normal. Instead of two adds there are now three that need to be dealt with. Again these can not be tanked as they apply a healing debuff, instead they need to be kited around the room. They can no be CC'ed but can be slowed, snared or rooted. In heroic mode they also throw out frost bombs which slow anyone over them and look a little too much like frost traps for many players. If you have a hunter using frost traps expect to be confused a bit

Also in heroic mode Obsidius can slow down the tank and know the tank down. This is not done in normal mode but as long as you have someone else kiting the adds, it is not really an issue. It is just to make sure that the tank is not really able to tank the boss and kite the adds all at once. It is there to force another player to kite.

Overall

The instance was pretty cool, especially if you liked the original Blackrock instances and raids.  It really felt like returning to the WoW of several years ago.

The fights in the instance are all fun and challenging, without being too hard for players just returning to WoW.  I especially like the use of varied mechanics throughout the instance.  By this I mean the first boss has a “get out” mechanic, the second a timing component, the third is about managing debuffs, and the fifth brings back kiting.  I see this as a great thing as it should be able to keep players’ interest as each fight is so different.

Gear wise and progression wise, expect the instance to be a step up on gear for most players.  The gear is itemized around the same as ICC 25 gear, so unless you are  a 25 person raid player, the gear will be an improvement over what you have.

Even though this instance is good on normal mode, I think it is much better on heroic. With all the varied mechanics in the instance, it is very challenging in the heroic version.