Magic Medallion

In A Link to the Past, a handful of destructive spells came in the form of three golden Medallions. Each of the spell Medallions targets every enemy on screen, but each have varying effects, and some enemies are immune to the effects of certain Medallions. All three spells center around using the Master Sword, and as such, they cannot be used if the Master Sword (or its upgraded versions) are unavailable.

The three Goddess Spells in Ocarina of Time could have originated from these Medallions; both are trios, are obtained outside of dungeons, and use up more Magic Power than any other items or abilities in their respective game.

The Legend of Zelda: Four Swords Adventures has versions of medallions with only one use. To use, a player holding the medallion simply tosses it.

Ether Medallion
The Ether Medallion is the first and arguably the easiest to obtain of all three, and can be found across a bridge east of Tower of Hera. A green tablet identical to the one found in front of Desert Palace appears here, and as before, Link requires the Book of Mudora to translate its message. It instructs Link to raise his Master Sword to heavens. Once he does so, the lightning-based spell is cast, the tablet is destroyed as a result, and the Ether Medallion falls from the sky into the young warrior's hands.

Ether attacks the atmosphere, as flying enemies appear most susceptible to its damage. Most enemies who aren't destroyed by the initial blast of lightning and aura are frozen, as if they were struck by the Ice Rod. Ether's atmosphere-altering capabilities can be used to clear the rain in Misery Mire.

Quake Medallion
At the mouth of the river north of Palace of Darkness, in a place known as the Lake of Ill Omen, lies a circle of stones in the water. By throwing a rock into this circle, Link will awaken a massive fish, who will offer the Quake Medallion in order to be left alone. Coincidentally, this is the only Medallion obtained without celestial origins, and is the only one Link doesn't activate upon receiving. The oddity of this Medallion could perhaps be to represent than Quake originates from the earth instead of the heavens.

Expectedly, Quake causes an Earthquake, resulting from Link thrusting the Master Sword into the ground below him. It only effects ground-bound enemies, generally either destroying them or turning them into weak Slime. Quake is needed to open the passage to Turtle Rock.

Bombos Medallion
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.