Felsteed

From the official World of Warcraft1 website:

The remote plains of Desolace were once home to a unique breed of horse too proud and wild to countenance riders. Yet it is precisely this willful conceit that enticed the elders of the Shadow Council to bind these majestic steeds to their service with dark rituals too horrific to perform by any but the most depraved of warlocks. Although they retain their imposing forms, these newly-christened felsteeds have become twisted with infernal energies, treading flames and breathing fire. Where their eyes once shone with exuberance and a zest for life, they now burn with hatred for the warlocks who corrupted them and anguish at the passing of the lives they once knew.

The Felsteed is a creature summoned by a Warlock in the computer game World of Warcraft. Acquired upon reaching level 40, it functions as a mount, enabling the Warlock to move at 160% his usual speed. Unlike most other classes, the Warlock has this Felsteed as a class specific mount that is received as a quest reward and, as such, is free (the Paladin is the only other class that receives a free, class specific, mount). This is in stark CONTRAST to the acquisition of mounts for any other class which is then race specific, instead of class specific, and typically costs 100gold (90gold for the training in Apprentice Riding and 10gold for the actual mount). Also, unlike other mounts, it appears as a spell rather than an item, and so does not take up any space in the character's inventory. It appears as a black horse with flaming hooves, eyes, and nostrils. Summoning a Felsteed requires a 3 second cast time and 100 mana.

As of the 1.12.1 patch, the profession "Apprentice Riding" is now included with the Felsteed.