Winged Guardian

The Winged Guardian serves both as a flying and a ground mount depending on the terrain. When you take to the skies astride a blazing, eagle-winged lion, your comrades will know you mean business. Serious business. The majestic Winged Guardian is a titan creation from Uldum that was designed to protect Azeroth’s most ancient secrets. This Guardian of the Titans will carry you across Azeroth as fast as your riding skill will take you.

Unlike the mounts from the World of Warcraft Trading Card Game, this mount is directly purchasable from Blizzard. Released on May 31, 2011, it is the second mount to ever be offered in this way, the first being the Celestial Steed.

Source
This item is available for purchase from the shop or the In-Game Store for $25 or €25. It was released on May 31, 2011.

Mount Journal
Unearthed recently in an ancient tomb, this mighty winged lion may have once served one of the ancient Tol'vir princes.

Light up the night on this blazing, eagle-winged lion.
 * In-Game Store

Part lion, part eagle, all business - ''When you take to the skies astride a blazing, eagle-winged lion, your comrades will know you mean business. Serious business. So saddle up, because this flying mount will travel as fast as your riding skill will take you.''
 * Blizzard Shop

Mail
Players are mailed this mount by :

Notes and trivia

 * Available only to players on realms located in North America, Europe, and Korea.
 * Players who purchase it receive a code similar to that of the loot cards. When you enter the code in your account all characters are mailed a copy of this pet, as well as any future characters you create.
 * When performing a mountspecial, this monster will let forth a gutteral growl and spread its flaming wings.
 * When it runs, it uses the gait of a gryphon and a sabrecat.
 * This mount is also the only mount to emit a ghostly roar when its owner summons it. Although it possesses that roar, the Spectral Tiger is also able to roar like a ghostly lion.
 * When it runs, walks or flies, it leaves behind a trail of flames from its wings. In addition, its mane, wing feathers, tail tuft and paws are covered in a small, but thick flame. If you look closely, you can see that its mane is tied into braids.

In Hearthstone
A Winged Guardian appears as HS Winged Guardian (boss) (one of the bosses) that can be encountered in the HS Tombs of Terror adventure in the Saviors of Uldum expansion for Hearthstone.

Winged Guardian is also a HS Winged Guardian (a rare druid card) in the HS Galakrond's Awakening adventure. Its flavor text reads: "Take these broken wings, be reborn, and learn to fly again."