All tiers of Tantrum gear are soul bound to the player. This is automatic and there's no way to unbind it. This form of soul binding does not mean "to keep on death", it means it belongs solely to the player. No one else can pick it up off the ground or out of chests. If somehow someone else gets a hold of your soul bound item, it will be removed from their inventory and placed in an imaginary storage container and waits there for you to retrieve it. To retrieve your 'lost' soul bound item(s), run the command /returnitems and it will open up this imaginary container where your item is waiting.