Update: You no longer need a Drakefire Amulet to enter Onyxia's Lair! I've left the guide up so old-timers can show their friends what they had to go through to fight Onyxia

The dragon Onyxia is the boss of a 40-man end-game raid in World of WarcraftTo enter her lair everyone in the raid needs a Drakefire Amulet, often called an "Onyxia key." Obtaining a Drakefire Amulet involves completing one of the longest quest chains in the gameIt differs depending on whether your character is Alliance or HordeThese are the steps required for Horde players

1Warlord's Command (LBRS)
At level 55 or higher you can get the "Warlord's Command" quest from Warlord GoretoothHe's at the top of a tower in Kargath in the Badlands and has no exclamation mark over his headYou will have to slay Highlord Omokk, War Master Voone, and Overlord Wyrmthalak with a 5-man group in Lower Blackrock SpireYou also have to recover some important documents which spawn randomly at one of the 3 bossesSince version 1.7, everyone on the quest can loot the documents

2Eitrigg's Wisdom
Upon completion of "Warlord's Command," Goretooth will ask you to speak with Eitrigg in Thrall's chamber, which is in the Valley of Wisdom in OrgrimmarEitrigg wants you to talk to Thrall, who gives you the next quest

3For the Horde (UBRS)
Here you should have a 10-man raid to kill Rend Blackhand in Upper Blackrock SpireRend is a little over halfway through the instance, and most raids going to UBRS want to go at least that farBring Rend's head back to Thrall in Orgrimmar

4What the Wind Carries
Thrall has some things to tell youAll you need to do is have a nice chat with him in his chamber to complete this quest

5The Champion of the Horde
Now you will be sent to find Rexxar, who travels through Desolace from the Stonetalon border to the Twin Colossals in Feralas, then turns around and heads back

6The Testament of Rexxar
Rexxar wants you to talk to Miranda the Hag in the Western PlaguelandsYou'll find her near Uther's Tomb, just south of the Ruins of Andorhal

7Oculus Illusions (UBRS)
Miranda sends you back to Upper Blackrock Spire to collect 20 Black Dragonspawn EyesThese drop for raid groups and are quite plentifulYou shouldn't have any problem getting enough unless almost everyone in your raid is on the quest, in which case you can always kill some Dragonspawn in the Rookery

8Emberstrife
After taking the Dragonspawn Eyes to Miranda, she will give you an Amulet of Draconic Subversion and tell you to speak with the dragon Emberstrife, who is in a cave on the southern perimeter of Dustwallow MarshWhen you use the Amulet, it will disguise you as a Black Scalebane so that you can talk to Emberstrife without being attackedMake sure you get the first 3 "Test of Skulls" quests before moving on

9Test of Skulls, Somnus
Each of these quests requires you to kill an elite dragon and take its head back to EmberstrifeA 5-man group is best for these quests, but with a good healer they can be done with lessIt's not always easy to find willing people to help out because there is a lot of travel involvedSomnus can be found on the east side of Swamp of Sorrows

10Test of Skulls, Chronalis
Chronalis is an elite dragon in Tanaris near the mountain on the east edge of the zoneYou'll probably have to kill a couple lower-level drakes to get to him

11Test of Skulls, Scryer
Scryer is in the back of the caves of Mazthoril southwest of Everlook in WinterspringIt's well-populated with elite dragonkin so be prepared to fight your way inOnce you have the heads of Somnus, Chronalis, and Scryer take them back to Emberstrife in Dustwallow Marsh

12Test of Skulls, Axtroz
When you reach Emberstrife you'll have to go back into dragon form using the Amulet to turn in the headsEmberstrife will then give you one more elite dragon to killThis time it's Axtroz, who is patrolling a canyon in Grim Batol on the east end of the Wetlands

13Ascension
Once you've taken Axtroz's head to Emberstrife in Dustwallow Marsh, you'll be sent back to Rexxar in Desolace, who will give you the last quest in the chain

14Blood of the Black Dragon Champion (UBRS)
Rexxar needs the blood of General Drakkisath from Upper Blackrock Spire to restore the Dull Drakefire AmuletDrakkisath is the last boss in the instance, and you'll need a 10-man raid to take him downAlthough you can't loot the blood without the quest, he only drops 2-4 blood each time, so depending on how many people in your group are on the quest, you may have to roll for itWhen you take the blood back to Rexxar he will give you your Drakefire Amulet, which grants you access to Onyxia's LairCongratulations!