Relentless Gladiator's Frost Wyrm

Source
This mount was awarded to the top 0.5% of arena teams per battlegroup at the end of Arena Season 7.

Mount Journal
In life, it could not be tamed, but necromancy and esoteric binding rituals have now combined to bend this indomitable creature to its rider's will.

Achievements
Qualifiers for this mount should also get the Feat of Strength Relentless Gladiator's Frost Wyrm (achievement).