You can use an action to throw this red and white ball, targeting a beast of the DM's approval within 20 ft. of you, the target is captured in the ball. As an action you can throw the ball to a space within 20 ft. of you, the trapped creature appears in that space, it is friendly to you and your allies and will even fight for you if you treat it good. Also, as a reaction when the creature drops to zero hit points, you can summon it back into the ball. It is immediately stabilized and starts a long rest.