Midnight is Lua error in package.lua at line 80: module 'Module:Factiongfx/faction_tip_link.json' not found. Attumen the Huntsman's personal mount. She is known as one of the (if not the) fastest and strongest existing horses. She is a neutral boss in Karazhan and attacking her starts the Attumen encounter.
Attumen can drop Midnight as a mount, as 
[Fiery Warhorse's Reins].