The Bloodthirsty Dreadwing mount is a Horde-only mount added in World of Warcraft path 8.1. This unique bat can be purchased for 750 x Honorbound Service Medals from Provisioner Mukra in Dazar'Alor.
In order to get this, you will need to obtain all 750 Honorbound Service Medals on the same character, then buy the mount from Provisioner Mukra. When you learn it, any character Horde can use it tough, as long as they are level 20+ of course.
The Honorbound Service Medals you need are tied to Warfront content, and there are currently four main ways to get these service medals:
1) Win a Warfront. Each new Warfront cycle will give you a quest to complete that Warfront. This quest gives you an item, as well as 15 x Honorbound Service Medals. Since it's tied to each Warfront cycle, you can only get this quest roughly every 2 weeks.
2) Participate in Faction Assaults. These pop up on the map pretty much every day, and you can "win" these by completing four World Quests, then do a short quest. Each of these give you 5 Honorbound Service Medals, potentially giving you 5 Service Medals daily.
3) Complete Warfront World Quests. When the Horde controls any Warfront zones, all level 120 Horde characters will get 5 World Quest in each controlled Warfront zone. These reset daily, so you can get 5x Honorbound Service Medals from each controlled zone per day.
4) Complete Honorbound Paragon Reputation. Every 10k reputation after having already gotten Exalted awards you with a Honorbound Paragon Cache. This includes some great items, as well as 20 x Honorbound Service Medals, so they are well worth the time it takes to farm extra rep!
As you can see, getting 750 Service Medals can take a while, even if you do all the possible things every day. So expect to spend at least a few months to grind for this, unless you are willing to log into the game at crazy times to complete all the Faction Assaults.