Crystal Ball

The Crystal Ball is a magical item that can reveal a targeted area, also unmasking invisible units. It lasts 10 seconds.

Third War
Grommash Hellscream found one during the invasion of Ashenvale by his Warsong clan during the Third War when he raided a dark troll settlement near the Ashenvale / Barrens borderline.

Legion
Years later, now known as the Astranaar Globe, it was found by Archmage Vargoth and eventually taken by the leader of the Tirisgarde.