Each artifact weapon has a hidden appearance associated with it. This post will cover how to obtain the Feral Druid hidden appearance.
I would like to acknowledge the comment contributors at WoW Head for this in depth detail which greatly helped me. I am also not the original author of the macros and scripts in this post. Credit to the authors in the comments at WoW Head.
What is the Feral Druid hidden artifact appearance?
Feral Druids get what is called Feather of the Moonspirit. It is a bird like appearance complete with feathers and a beak for your Cat Form. Pretty much identical to the cat mobs in Azsuna.