There have been stories of the legendary Spheres of Monster Storage. These are small spheres (small enough to store in your pocket), half red half white, with a button on one side. Once you have reduced the monster to single digit hit points you can engage in a contest of skill (Animal Handling vs Athletics/Acrobatics) to capture it and imprison it inside the sphere. You cannot capture an unconscious monster.
Once captured, you can release the monster by pressing the button on the side of the sphere and speaking the command phrase "I choose you" and engaging in another Animal Handling vs the monsters Wisdom saving throw to control it.
Not everyone is worthy of wielding the spheres. Only those whose goal is to be the very best, like no one ever was. You must quest across the land, searching far and wide to claim the power inside.