Onyxia Key (Horde)

This might not be of any use, but I see it as a try for me to write and practise

Step 1:

First you have to travel to Kargath in Badlands and go to a tower not long away from where you landed if you flew. In this tower there is a guy called Warlord Goretooth. Talk to him and go trough his conversation you will then receive a letter. Warlord Goretooth's Command. (I think it was a letter) Right-click on the letter and you will receive a quest, Warlord's Command.

Step 2:

In this quest you have to travel to Lower Blackrock Spire. As Jame has written a wonderful guide to this place, why not use it? http://www.wow-pro.com/node/593
When you have completed Warlord's Command you will receive the quest, Eitrigg's Wisdom.

Step 3:

Travel to Orgrimmar and go to Thrall's Chamber and talk to his adviser, Eitrigg (a speech bubble) and then complete the quest at Thrall, he will give you the quest, For the Horde!.

Now you have to travel to Upper Blackrock Spire and kill Warchief Rend Blackhand. Just jump on to a normal UBRS raid, as Rend is not able to bypass. When you complete the quest, everyone in Orgrimmar will receive a buff.

Step 4:

Thrall asks you to seek out Rexxar who roams from north Feralas, through Desolace, and into southern Stonetalon Mountains. Rexxar will give you the quest, The Testament of Rexxar.

Now you have to deliver Rexxar's Testament to Myranda the Hag in Western Plaguelands. Myranda the Hag is located near Uther's tomb, south of Andorhal, standing on a tree stump. She will give you the quest, Oculus Illusions.

Step 5:

Once again you have to go to UBRS and get some Black Dragonspawn Eyes from the dragnkins inside. They drop 1-2 at a time and are common. It should be enough with one run When you turn in the quest you will get an Amulet of Draconic Subversion and the quest, Emberstrife.

Step 6:

Travel to Emberstrife's Den in Dustwallow Marsh, it´s the cave at the cliff to the very south. The Amulet of Draconic Subversion will transform you into a Black Scalebane once inside Emberstrife's Den. While disguised, speak to Emberstrife. He will behave as an NPC. He will give you three quests called The Test of Skulls, Skryer/Somnus/Chronalis.

1. Go to Winterspring with a group of five people and enter the caves of Maztoril, south of Everlook, work your way in and kill Scryer.

2. Somnus can be found in the Swamp of Sorrows, wandering in an arch up and down the zone between the Pool of Tears and the beach.

3. Chronalis can be found in Tanaris along the east edge of the zone is a mountain, Enter the area and you will find two low level dragons and then, Chronalis. Kill him and return to Emberstrife and get the quest, The Test of Skulls, Axtroz.

Step 7:

Axtroz can be found in Wetlands, at the Dragonmaw Gates region, the curved valley area in the east side of the zone. Travel down the valley and you will find Axtroz. Kill him and return to Emberstrife to receive the quest, Ascension...

Step 8:

Now you have to find Rexxar again. He will give you the quest, Blood of the Black Dragon Champion.

Now you have to travel to UBRS again and this time kill General Drakkisath. Kill him, and get the blood of him.

NOTE: General Drakkisath only drops 2-3 bloods each kill.

Step 9:

Return to Rexxar and you will receive the Drakefire Amulet, a necklace.

Keep the Drakefire Amulet in your inventory to be allowed access into Onyxia's Lair.

You are now eligible to raid Onyxia, Brood Mother of the Black Dragonflight!