Uroe, Harbinger of Terror

Uroe, Harbinger of Terror is a battle axe infused with the power of lightning. It was used by Lei Shen, the Thunder King, during his reign as emperor. After his death it was lost in the Vale of Eternal Blossoms. It was found by adventurers aligned with the Golden Lotus before being stolen by the forces of Zhao-Jin the Bloodletter and returned to the recently resurrected Thunder King. Lei Shen used the axe in the first and third phases of his final battle.

Source
This item drops from Lei Shen in Throne of Thunder.