Warcraft Twitch Channel 3D Printing and Building Mysterious Object

The Warcraft Twitch channel has just gone live under the title Camelot_reveal v2_final.mp4 and appears to be 3D printing a mysterious object.

WoW: Forever launches in just over 6 hours, and the Warcraft Twitch channel has suddenly gone live. The stream is playing WoW: Forever music and showing parts of something being 3D printed and built.

Warcraft — Camelot_reveal v2_final.mp4

Playing World of Warcraft for 10,099 viewers.

What could they be building?