Perhaps you will be interested
Invincible is a flying mount obtained when defeating the Lich King "in his strongest form"on heroic difficulty in 25-player mode only. It can also be listed on the Black Market Auction House.
Here you can buy Invincibles Reins for EU or US Servers.
You'll get guide for getting Invincibles Reins
• You'll be able to get Invincibles Reins
• Invincibles Reins mount
• After patch 10.2 might will need character transfer for access to BMAH