The Bombos Medallion can be found in Misery Mire, via a green tablet which can only be read with the Book of Mudora. As with Ether, the spell is cast once Link's sword is raised, the tablet is broken afterwards, and the Medallion drops from an unknown origin in the sky.
The Bombos Medallion is the last which can be obtained, and is fittingly the most destructively powerful of three. With an enchanted Spin Attack, Link sends out a ring of fire followed by a series of small explosions in all directions. This causes all foes to become lit aflame, as if they have been struck with the Fire Rod, and destroys all its targets. Bombos does not simply disable its targets like the other two Medallions, and targets more enemy types than either!!!