Wonder Boy in Monster World/Magic

Shion can learn a couple of different magic spells, each with various different effects. Each magic spell has a limited amount of uses, displayed by the amount of blue crystals under the spell's name in the Pause Menu. When your magic is used up, you can rest at an inn to replenish it. Also some higher level monsters drop blue chrystals. Picking them up will replenish your magic as well.

Fire Storm
Summons a stream of 7 small, minor-damage fireballs that home in on nearby enemies. When only a single enemy is nearby, it will be attacked by the full barrage, quickly adding up the damage. Even if all 7 fireballs hit their target, they won't always give the full damage.
 * 1) fireball gives the same damage as 2.5 hits with the Gradius
 * 2) fireballs gives the same damage as 5 hits with the Gradius
 * 3) fireballs gives the same damage as 7.5 hits with the Gradius
 * 4) fireballs gives the same damage as 10 hits with the Gradius
 * 5) fireballs gives the same damage as 12.5 hits with the Gradius
 * 6) fireballs gives the same damage as 15 hits with the Gradius
 * 7) fireballs gives the same damage as 17.5 hits with the Gradius

Thunder
Causes all enemies on screen to be attacked by a bolt of lightning for decent damage. This will defeat many minor enemies in one blow.
 * Gives the same damage as 20 hits with the Gradius

Quake aka Explosion
Shakes the earth, doing high damage to all enemies on screen touching the ground. Flying, swimming or jumping enemies will not be affected.
 * Gives the same damage as 20 hits with the Gradius

Shield
Causes Shion to be fully protected by a magical shield for a limited amount of time. When Shion is hit, the shield will block any damage, steadily decreasing the shield's time limit. You can not use items or any other type of magic while Shield Magic is active.

Power
Doubles Shion's weapon attack power for a limited amount of time. Similar to the Shield magic, the Power magic's time limit will decrease more steadily when you cause damage to an opponent. You can not use items or any other kind of magic while Power Magic is active. First found in the Pyramid.

Return
Warps Shion to the inn you last saved your game at. Can only be used once before it needs to be replenished. Found just before meeting Poseidon. If you've never stayed at an inn, you will instead be sent back to your house at the start of the game. The only magic limited to a maximum of 1.