This monster of a mount comes from Nakk the Thunderer in Nagrand (Draenor). He is one of the 7 rare spawn mounts available in Draenor.
There is a 100% drop rate on this mount and everyone who tags him will receive one.
Nakk himself can be found at one of 5 spawn points – Cords 61.14 – 64.20 – 60.32 – 54.35 – 49.33. He has a 19 – 30 hour spawn time.
He is surrounded by Ironhide Bulls so if you want to avoid being knocked back into more trouble I would clear the area a little. Nakk himself is a level 100 elite and has around 4892k hp. The fight is very easy at 110 and is over in a few seconds. I personally put out a call in general chat to see if there was anyone else camping or just in the vicinity that might like to nab the mount as well.