Felsteed

Corrupted by demonic power and once forced to serve the Shadow Council.

Riding Requirements:

This mount is available to all eligible characters on your account.
Level 10
Apprentice Riding
Warlocks only

Source:

Warlock Trainers.

Notes:

This is the first warlock class mount. By default its flames are red-orange, but they'll appear green-yellow if the warlock is using The Codex of Xerrath.

Introduced in:

Patch 1.0

Travel Mode:

Ground (+60% or +100% speed)

Speed depends on your riding skill.

More info on Wowhead:

Felsteed