Use: Teaches you how to summon this mount. Can only be summoned in Outland or Northrend. This is a very fast mount.
Azure Drake
Source
This item has an extremely low (1% - 2%) chance to be found inside Alexstrasza's Gift after defeating Malygos in The Eye of Eternity. It can drop in either the 10-player or 25-player version of the instance.
Patch changes
Patch 4.0.3 (15-Nov-2010): Reins of the Azure Drake will once again drop in the 25-man version only.
Hotfix (2010-01-05): "...The Reins of the Azure Drake will have a chance of dropping in both 10- and 25-player versions of The Eye of Eternity."