Basic overview and location

Hellfire Citadel (located in middle of Hellfire Peninsula, Outland) served as Horde base during the First and Second Wars. Now it is inhabited by Maghteridon.

On the blasted world of Outland, within the heart of Hellfire Peninsula stands Hellfire Citadel, a nearly impenetrable bastion that served as the Horde's base of operations throughout the First and Second Wars, although Khadgar's expedition took control of the citadel shortly after first setting foot on Draenor. For years after Draenor's destruction this gargantuan fortress was thought to be abandoned...

Until recently.

Though much of Draenor was shattered by the reckless Ner'zhul, the Hellfire Citadel remains intact– inhabited now by marauding bands of red, furious fel orcs. Though the presence of this new, savage breed presents something of a mystery, what's far more disconcerting is that the numbers of these fel orcs seem to be growing.

Despite Thrall and Grom Hellscream's successful bid to end the Horde's corruption by slaying Mannoroth, reports indicate that the barbaric orcs of Hellfire Citadel have somehow managed to find a new source of corruption to fuel their primitive bloodlust.

Whatever authority these orcs answer to is unknown, although it is a strongly held belief that they are not working for the Burning Legion.

Perhaps the most unsettling news to come from Outland are the accounts of thunderous, savage cries issuing from somewhere deep beneath the citadel. Many have begun to wonder if these unearthly outbursts are somehow connected to the corrupted fel orcs and their growing numbers. Unfortunately those questions will have to remain unanswered.

• Levels: 60-70
• Players: 5-25
• Layout: 4 Wings
  • Hellfire Ramparts (Level 60-62 mobs, 5 player groups) - enter through bridge which is accesible from ground between Hellfire Citadel and Honor Hold/Thrallmar (or you can jump down from The Blood Furnaces place)
  • The Blood Furnaces (Level 61-63 mobs, 5 player groups) - enter through stairs on left (south) side of Hellfire Citadel 
  • The Shattered Halls (Level 70-72 mobs, 5 player groups) - enter through the same path as Hellfire Ramparts. Requires a key to access (drops from final boss in The Blood Furnaces, you must get a quest in Shadowmoon Valley frin Snutg Gorlunk)
  • Magtheridon's Lair (Level 70 mobs, 25 player raid, similar to Onyxia's Lair) - enter from west side of Hellfire Citadel, just down the hill 

Most of the info is taken from bc.worldofwar.net. Some texts are my contribution, other texts are contribution of other volunteer of WorldOfWar BC Wiki.

Hellfire Ramparts - (Level 60-62 mobs, 5 player groups)

Watchkeeper Gargolmar

The first boss of The Ramparts wing of Hellfire Citadel

Level (Normal): 62 Elite
Level (Heroic): 72 Elite
Type: Humanoid

Abilities

Surge - randomly charges party members for minor damage (about 600 on cloth) and knocking them down.
Unprepared - at 50% health Gargolmar will ask his minions for healing.

Strategy

This is an easy fight. First thing that needs to be done is clear the majority of the trash around his patrol to avoid adds and make sure the trash is pulled back to the party. When engaging the boss, first priority is to take down the two Healers while Watchkeeper Gargolmar is being tanked. While you are killing the healers they will try and heal themselves and or Watchkeeper Gargolmar, stop them if at all possible because they heal for a lot. Alternatively if you have 2 mages, you can sheep the healers, kill Watchkeeper and then finish them off. Or you can keep them feared with a warlock.

Watchkeeper Gargolmar will charge the furthest person from him randomly during the fight. It will hit cloth pretty hard. Keep someone in Mail or Plate armor out there to take the charge, just like the Bloodlord Mandokir fight in Zul'Gurub, other than that just DPS him down.

Nazan and Vazruden

Vazruden and Nazan make up the second boss encounter in the Hellfire Ramparts wing of Hellfire Citadel.

Nazan :
Level (Normal): 62 Elite
Level (Heroic): 72 Elite
Type: Dragonkin

Vazruden:
Level (Normal): 62 Elite
Level (Heroic): 72 Elite
Type: Humanoid

Abilities

Attacks from the sky with AoE fireballs
Lands when Vazruden is Low HP/Dead
To be faced Away from the rest of the group
Is best fought in the large area
Will Create AoE Fire rings.

Along with Vazruden these 2 make up one of the 2 last bosses of Hellfire Ramparts, and attack together, sortof. You'll also want any Fire Resist gear for phase 2.

The fight begins with the 2 Guards deaths at the bottom of the ramp (Not the Patrolling ones), so be fully prepared before engaging them. After they Die, Nazan Will drop off Vazruden in the centre of the circular area, and then re-take to the skies.

Tank/Spank Vazruden, and get him out of the way fast, whilst keeping an eye out for Nazan firing AoE fireballs from above.

When Vazruden Dies/Gets low HP, Nazan will land and (usually) head straight for your healer, as he's the only one thats accumalating agro on him, so keep them at the back of the group, and taunt Nazan fast. It's also a good idea to pop PW:S if you're a priest at this point, just incase.

Face Nazan away from the rest of the group, away from his AoE Fire breath, and try not to steal agro. Fire AoE rings will also appear on the ground where he breaths, so stay out of them, and tank him out of them. It's best to fight this bit in the big ring so you can see what is going on.

Alternate Tactic 1

Nazan can be targeted before he lands, so one way you can do this fight is tank Vazruden but don't kill him, and range down Nazan first, with will mean you have to deal with much less of his powerful attacks. Nazan still landed when he was about to die but the tank can easily taunt him whilst you finish him off. I have tried it both ways and if you have the ranged DPS for it this way seams easier.

Omor the Unscarred

The third boss in the Hellfire Ramparts wing of Hellfire Citadel

Level(normal): 62 elite
Level(heroic): 72 elite
Type: Demon

Abilities

Treacherous Aura – Curse, periodically inflicting 360-440 shadow damage to friendly targets within 15 yards. It can be removed.
Summon Fiendish Hound – Throughout the fight he will summon his pet fel hunter which is not graced with the golden dragon.

Strategy

He has two guards at the entrance to his room, they can be pulled separately from him. Omor himself is a pretty straight forward fight. During the fight he'll spawn felhounds that usually go straight for healers but die very easily. Felhounds have less than 2k hp. When he has less than 20% hp he starts reflecting all spells every once in a while. Watch out, as a Presence of Mind-Combustion-Pyroblast combo REFLECTED can hurt quite a lot. He can also knock you up in the air, then juggle you with Shadow Whip.

It helps to have a curse remover for this fight although not needed if you are paying attention. Omor puts a curse on a random target that does damage to any around them but not to the cursed target. This curse can be removed or you can move the cursed person away from the group and let the curse wear off.

Randomly during the fight Omor will summon Fel Hounds. These creatures have very low hit points and need to be taken out before they get to a healer.

He has the ability to toss someone around in the air with a Shadow Whip. Rarely does he do this but be aware of the ability. Once the person is let go they will fall and take a good amount of fall damage.(edit: After the most recent push, he seems to do his Shadow Whip much more often, possibly only to MT.)

Just watch for the abilities and DPS him down

The Blood Furnaces - (Level 61-63 mobs, 5 player groups)

The Maker

First boss of the Blood Furnace wing of Hellfire Citadel

Level (Normal): 62 Elite
Level (Heroic): 71 Elite
Type: Undead

Abilities

Knockback – knocks back all in melee range.
Mind Control – randomly targeted mind control.
Acid Spray – short-range poison cone

Strategy

He's a fairly simple encounter; most groups of level 60ish characters should have no troubles with him. He doesn't hit particularly hard and can generally be DPS zerged down pretty quickly. His Mind Control cannot be removed so it's a good idea to sheep any players that are affected by it

Broggok

Second boss of the Blood Furnace wing of the Hellfire Citadel

Abilities

AoE Poison Bolt – the bolt hits for about 650-700 damage on impact and has a DoT effect that ticks for 320-380 damage every 3 seconds. It can be removed.
Poison Cloud – Broggok will drop these beneath him during the fight; it ticks for about 650 a tick but is stationary.

Strategy

The encounter starts by pulling a lever that releases four increasingly difficult waves of Fel Orcs. Once each wave is defeated (or enough time has passed since the last wave was released) the next wave will come immediately. The first wave consists of three non-elite Fel Orcs, the second of three non-elites and one elite Nascent Fel Orc, the third has two elites and two non-elites, and the fourth and final wave has three elites and two non-elite Fel Orcs. Once the fourth wave is defeated, Broggok will come immediately.

The Broggok encounter is actually fairly difficult and heavily reliant on crowd-control to survive the four waves of Fel Orcs that come before Broggok himself. Most players thus far have found it helpful to have Priests or Warlocks use AoE Fear abilities as each wave emerges, to give the group a little more time to prepare. The nonelite fel orcs are fairly docile and can be DPS zerged down pretty quickly. The elites, however, hit rather hard and have an off-target Intercept ability that makes them difficult to keep under control. It is generally wise to crowd control as many of the elites as possible, offtank or stunlock any remaining elites, and use focus fire to kill them as quickly as possible to conserve healer mana.

Once the fourth wave of orcs is dead, Broggok himself will enter the room. He isn't particularly difficult - if you can survive the fourth wave of orcs, Broggok should be no problem. He drops rings of poison on the ground directly beneath him which will slowly expand outward; the tank will need to move him to avoid taking damage. He also has an AoE poison bolt with a DoT component that will need to be dispelled.

It is possible to leave one orc from the final wave crowd controlled while the group heals up and regenerates mana, but usually not necessary.

Keli'dan the Breaker

Third boss of the Blood Furnace wing of Hellfire Citadel. He drops the key to the Shattered Halls wing.

Abilities

Cone Shadow Bolts – A large cone shaped attack launching Shadow Bolts for 2000-3000 damage.
Blastwave – A charged Blastwave dealing 4000-4500 damage.
Corruption – Magic, DoT shadow damage

Strategy

The Keli'dan encounter is composed of two phases. First, Keli'dan's five warlock companions must be killed. They have little HP, and can generally be killed quickly using AoE. However, they will cast a two-minute duration magic debuff on random party members that increases Shadow damage taken by 1000. Most groups make sure to bring a Priest or Paladin for this encounter, however it is also possible to keep one Warlock crowd-controlled while waiting for the debuff to expire. The debuff also has a small cast time, so it can be interrupted if you catch it in time.

Once the last Warlock is dead, Keli'dan will yell and come after the party. He has a cone-shaped AoE Shadowbolt attack that hits for 2-3k, so it is generally wise to have the tank hold him facing away from the rest of the group. He will also occasionally go immune to all damage and stand in place, then after a couple seconds explode for 4-5k damage to anyone in close range. The tank (and any melee DPS) should run out when he yells to avoid this attack.

The Shattered Halls - (Level 70-72 mobs, 5 player groups)

In order to be allowed to access, players must get a key. The quest to make it begins in Shadowmoon Valley with Smith Gorlunk.

Grand Warlock Nethekurse

The first boss in the Shattered Halls wing of Hellfire Citadel

Abilities

Death Coil – Deals about 1300-2000 shadow damage and fears target for 4 seconds. Also heals Nethekurse for 2600 health.
Lesser Shadow Fissure – Opens a shadow fissure beneath party members, deals 1000 shadow damage a second.
Dark Spin – At 20% health, Nethekurse will start his Dark Spin hits all targets near him with physical damage and randomly shoots Shadow Bolts every couple seconds which hit for about 1000-1500 damage.

Strategy

When you approach Grand Warlock Nethekurse, he will have 3 non-elite Fel Converts standing in front of him. After the 3rd of these are killed (the order does not matter), Nethekurse will attack the group.

Throughout the fight, he will place down 'void zones' that will begin to do 1000 Shadow damage per second after 1 second of being placed. Moving out of these as soon as possible is advisable for everyone including the tank.

He will also Death Coil random people which will do 2000 Shadow damage to the person hit, fear them for 4 seconds, and heal Nethekurse (presumably for 2000 HP).

At around 20% HP, Nethekurse will engage his 'Dark Spin' ability, in which he will begin to hit anyone directly around him for 2000 Physical damage and spit out Shadowbolts at random people in the group in rapid succession. The Shadowbolts hit for around 1500 Shadow Damage, and it is best to burn his remaining HP as quick as possible to limit deaths and a possible wipe.

Warbringer O'mrogg

The second boss in the Shattered Halls wing of Hellfire Citadel

Abilities

Thunderclap – AoE deals 800-1000 nature damage, leaves behind a Magic debuff Attack speed and Movement speed reduced by 35%.
Blast Wave/Burning Maul – When O’mrogg’s maul begins burning he deals about 1000 fire damage in melee and sets up to cast his Blast Wave which deals 2500-3000, he will do a second Blast Wave a few seconds later.
AoE Fear – Magic, does a shout and fears all in earshot.

Strategy

O'mrogg is a two headed ogre boss fight with a twist, he is immune to taunt and regularly does an aggro dump. Everyone should spread out in this fight and watch their aggro management, O'mrogg does a powerful blast wave AOE that hits for around 2k which can be lethal, ontop of that he also does an AOE fear, you will regularly find your tank loose aggro in this fight and so other classes will have to tank him, just hope it's not one of your healers!

Kargath Bladefist

The final boss of the Shattered Halls wing of Hellfire Citadel

Abilities

Guard-fest – Reaver, Heathen, and Sharpshooter guards will come pouring down from the North to help their lord.
Blade Dance – Kargath will begin bouncing around his room cleaving randomly everywhere for physical damage.

Strategy

Bladefist is a fairly simple fight but none the less, still has some key points to remember

He hits plate for about 700, which is fairly weak
He does no spell damage so Amplify Magic is a great help in this fight

Every few seconds he'll spawn a non-elite add which runs down the hallway, what kind of mob the add is is random but they have little health and can be dps'd down quickly

Every 35 seconds (?) Kargath will do a blade dance where he hits dashes at high speed between random targets dealing 1k cleave damage with a little aoe.

To take him down you can deal with the adds, ignore them and do straight DPS to Bladefist, or kill the adds as they come, it is important everyone spreads out and staying away from the center because the Blade Dance can be a killer if ignored. He has alot of health, but is a fairly simple encounter.

Magtheridon's Lair - (Level 70 mobs, 25 player raid, similar to Onyxia's Lair)

No info available yet.