Blackwater Bonecrusher

Best keep those bones to yourself if you don't want them crushed.

Riding Requirements:

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

Source:

Blackwater Trove.

Notes:

According to the database, this mount can be found in a Blackwater Trove loot box, which can be obtained from Boatswain Hardee upon reaching Exalted with Blackwater Cartel in Undermine. We haven't yet confirmed how these 'Trove' lootboxes work, but they seem to be rewards from an Emissary reputation system, where you're awarded a new box each time you perform a set number of tasks or gain a certain amount of reputation with that faction.