While Donned, worn on the arm, it gives you the ability to cast the Infestation Cantrip.
While Doffed, and worn on the back, stating the command word will cause the shield to split in half, and giant insectoid wings sprout from it, giving you a fly speed equal to your land speed for 60 minutes, or until the shield is removed from your back. The minutes do not need to be used consecutively.