Item would be far too oppressive, even as a 6200 item. Unsecured souls are unsecured for a reason, they are the player's souls but you can kill them if you want the souls. Ontop of that, an item that requires you to also own the item to counter it is awful design, when designing an item / ability it is most important to consider if its fun to fight against, rather than fun to use. This is because you are much more likely to have the item used against YOU rather than you use it against the enemy.