Why Aronen has Frostmourne?

Why Aronen has Frostmourne? Not blizzlike...

https://imgur.com/M2GND3g

Are you sure it's not just a visual client side bug? I remember that because i was playing with my same wow wotlk client on another server this one time as well, I downloaded some of their stuff, and some textures changed; a helmet looked like LK's helmet, even though it was a cloth green