Swirling Green Orb of Thunder

From Ardrana

The Swirling Green Orb of Thunder is a mysterious artifact that is currently possessed by Goalec 1, the lord of the town of Gheldren. The object is a sphere approximately six inches in diameter, weighing about fifteen pounds, and is colored an opaque green, similar to jade, with swirls of other colors that play across its surface. It sits in a case on a table in the great hall of the Palace of The Goalec.

The bards of western Tanilon tell of Goalec using it during the Wars of Arin, when he would roll it across the landscape at oncoming enemies, and it would grow in size and roll over them, crushing them underneath. As it rolled, it made a great rumbling noise, like thunder rolling across the sky. What other powers it may have remain a mystery.