This shield drops from The Legion Commander of the Void during the monster mission "Out with the Old" which is started by giving a Bristlebane's Ticket of Admission to a silly puppet in Kithicor Forest. The ticket was gained by various Halloween tasks.
When leaving the monster mission, the shield converts to:
Splintered Shield of the Void
Fractured Shield of the Void
Split Shield of the Void
Cracked Shield of the Void
Chipped Shield of the Void
Lesser Shield of the Void
Shield of the Void