|Not yet implemented!
Brood of Onyxia is an extremely fast (310%) flying mount that drops from Onyxia.
Patch 3.2.2 (2009-09-22): "Now, in honor of the World of Warcraft 5-year anniversary, the dreaded brood mother Onyxia is being revamped to make a return to the forefront of Azeroth, as part of our big plans for the upcoming 3.2.2 content patch.
This permanent update to Onyxia will convert the dungeon into 10- and 25-player modes. We will be adding new items to Onyxia's loot table... There will be a special new item too: a normal drake-sized 310% speed flying mount modeled after Onyxia herself called Brood of Onyxia." (Source)