Dragonwrath, Tarecgosa's Rest - Wowpedia - Your wiki guide to the World of Warcraft
Now that most Legendaries are moggable, I think it's high time that Dragonwrath got a special quest line to obtain a mount based on the 'use' feature of the staff + Dragonflight :
Warlocks progress in their "Dragonwrath, Tarecgosa's Rest" questline - Chapter 2
Firelands Legendary Staff: Get Ready! - Mana Obscura
Dragonwrath Legendary Weapon Transmogrification Guide - World of Warcraft - Icy Veins