Mystic Runesaber

It does in fact fly, spectral wings come out of the purple circles near the front shoulder blades of the mount, much like the MoP CE mount.

The [item=122469] is the 10th store mount to be added to the game. It can be purchased for $25 in the ingame shop.
Previous store mounts in the order they were added:

1. 
   
2. [item=54811] (Patch 3.3)
3. 
   
4. [item=69846] (Patch 4.1)
5. 
   
6. [item=78924] (Patch 4.3)
7. 
   
8. [item=92724] (Patch 5.1)
9. 
   
10. [item=95341] (Patch 5.3)
11. 
    
12. [item=97989] (Patch 5.4.1)
13. 
    
14. [item=107951] (Patch 5.4.2)
15. 
    
16. [item=112326] (Patch 5.4.8)
17. 
    
18. [item=112327] (Patch 6.0.3)
19. 
    

Additional information about all mounts added in Warlords of Draenor can be found in the Warlords of Draenor Mount Collector's Guide

In the PTR i see the following information

Name : Mystic Runesaber

How to get it : In-Game Shop

Mount info : Infused with arcane power, the Mystic Runesaber has long been hidden by chaotic nether energies. Recently they have emerged from the shadows in search of ley lines to sate their thirst for magic.