Plagued Proto-Drake

Bred specifically to honor those heroes who showed significant courage and persistence facing the dangers in Northrend.

Riding Requirements:

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

Source:

The Black Market Auction House (rarely)

Notes:

This mount was originally the reward for the achievement Glory of the Raider (10 player), but was retired in Patch 3.1. It returned as a rare Black Market Auction item in Mists of Pandaria.

Introduced in:

Patch 3.0

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:

Blue Proto-Drake

Green Proto-Drake

Red Proto-Drake

Time-Lost Proto-Drake

Violet Proto-Drake

Black Proto-Drake

More info on Wowhead:

Plagued Proto-Drake taught by Reins of the Plagued Proto-Drake