Alliance Onyxia Quest

Dragonkin Menace (Burning Steppes) ->

The True Masters (part 1, Redridge) ->

The True Masters (part 2, SW) ->

The True Masters (part 3, back to Redridge) ->

The True Masters (part 4, back to Morgan's Vigil in Burning Steppes) -> talk to Ragged John -> talk to marshal Maxwell ->

Marshall Windsor -> Abandoned Hope.

Next step begins when you find a Crumpled Note off random drop in BRD. Take it back to Marshall Windsor and get A Shred of Hope -> Jail Break ->

Stormwind Rendevous ->

The Great Masquerade,

Finishing The Great Masquerade yields a "Fragment of the Dragon's Eye." You then have to travel to Winterspring and speak with Haleh, who is reached by stepping on the runes at the back of the cave in Mazorthil. She sends you to kill General Drakkisath in upper Blackrock Spire, who you really will need a raid for. You need his blood, and he only drops one for the entire raid (update: reported to be dropping as many as 4 bloods per raid now). Once you have that, Haleh will give you the Drakefire Amulet, which serves as the key to Onyxia's Lair.