Antoran Gloomhound

Sargeras' own hound was maybe once a felstalker, but over the years the Dark Titan reforged and reshaped his companion into something much more powerful. When, at last, he was pleased with his creation, he set about creating more of the hounds, and imbuing them with shadow and flame.

Riding Requirements:

This mount is available to all eligible characters on your account.
Level 10
Apprentice Riding (ground)
Expert Riding (flying)

Source:

Achievement: Glory of the Argus Raider

Notes:

This shadowy demon is the raid meta-achievement reward for "Antorus, the Burning Throne".

Introduced in:

Patch 7.3.2

Travel Mode:

Ground (+60% or +100% speed)
Flying (+150%, +280% or +310% speed)

Speed depends on your riding skill.

Other Mounts Using the Same Model:

Antoran Charhound

More info on Wowhead:

Antoran Gloomhound taught by Antoran Gloomhound