Ensorcelled Everwyrm

For those wondering you click the orb on the back of the mount.

Beware though, if you have multiple licences under the one account it may very well be limited to that licence that you made the purchase for. I have 2 licences and can only access the NPC on the licence I made the purchase for even though I can access the mount on both licences.

I will update if I find out if this is an error or an intended thing that they forgot to tell us about.

it took me way too long to figure this out, so here's the dummies guide to starting the quest:

1) Ride the mount.
2) Fly down to the ground if you're in the air.
3) Click the orb on its tail.
4) An NPC questgiver will slowly appear on the ground next to you, talk to him.

If you want this mount, go and pre-purchase "Shadowland" Heroic edition as it is part of the bundle.