From the World of Warcraft website:
After years of lurking in her lair, battling brave adventurers who travelled from afar, Onyxia has been reborn -- and she’s stronger than ever before. To commemorate the upcoming fifth anniversary of World of Warcraft, the classic Onyxia raid encounter has been updated in the newly released patch 3.2.2.
- Onyxia has been retuned to offer new challenges to level-80 players (in both 10- and 25-player modes) while keeping the fundamental experience of fighting her intact. Beware the Deep Breaths!
- Onyxia will now drop new level-80 gear featuring the aesthetics of loot from the original encounter.
- The luckiest adventurers will have a chance to receive the Brood of Onyxia, a very rare 310%-speed mount modeled after the Brood Mother herself.