Ultima IV: Quest of the Avatar/Magic

Classes and MP
The Shepherd has no Magic Points, but in the NES port she is the only character who can use the Sheep Flute, an item that casts the Sleep spell on all opponents.

Still in the NES version, when the Stranger becomes an Avatar, his/her maximum MP promptly becomes 99. This holds true for every profession (in the subsequent episodes of Ultima, the Avatar will always be the character with the highest MP).

Reagents

 * '' See also the Britannian Yellow Pages #Apothecaries.

Six reagents can be purchased in every apothecary shop, but the remaining two are the subject of side quests.

In the spell lists below, the following abbreviations and prices are used for the reagents:

Spell list
In the table below, spells are grouped by type, then sorted by the gold cost of reagents. Indeed, what determines the availability of a spell are not magic points, but the gold to buy reagents. The GP cost of reagents does not consider Fungus and Manroot, that can be obtained for free.

Prompt specifies whether a spell is available since the beginning of the game ("yes") or if the characters should find something during the game (the recipe and/or some rare reagents). Three spell prompts are labeled as "new mix": the manual describes a recipe, but the characters can find a better recipe to cast them in the game. In the SMS port, instead, two of those recipes (plus a third one) are completely omitted from the manual, and the player can learn it from the game only.

Spell Types:
 * Healing: spells that can be used both during and after battle (exception: Resurrect);
 * Field: spells that can only be used outside battle;
 * Support: battle spells that target the allies;
 * Disable: battle spells that target the enemies but deal no damage;
 * Attack: battle spells that damage the enemies.

In the recipes, the reagents are sorted from the most expensive to the cheapest.

NES spell list
In the NES port, the recipes and the price of reagents are different. Furthermore, four spells were removed: Undead (no enemy sets), Open (no trapped chests), Up and Down (game breakers). On the other hand, three new spells were introduced, bringing the total to 25: Reflect, Squish and Defeat.

Prompt specifies whether a spell is available since the beginning of the game ("yes") or if the characters should find something during the game (the recipe and/or some rare reagents). After one or more characters told you about a new spell, it can be learned by going to "Spells Unlimited" in Moonglow, and telling the shop owner the proper ingredients.

In the original versions each of the 26 spells names start with a different letter. In the NES version some spell names were modified: for this reason, some spell names in the table below are preceded by the initial letter of the original and a slash (e.g. the original "Resurrect" spell is listed in the table below as "R/Life").

Healing spells

 * Cure poison: necessary; at game start, the Stranger starts with enough reagents to mix three of them; in battle, use it after all poisonous enemies have been defeated.
 * Heal: an emergency spell; otherwise, camping or resting at an inn restores more health to all companions (and all MP) for a similar price.
 * Resurrect/Life: sometimes necessary; highly recommended in Dungeon Hythloth.

Field spells

 * Open: useless; use "Cure poison" instead, that costs the same MP & GP, but is used only after a character actually got poisoned. Both trapped chests and this spell were omitted from the NES port.
 * Dispel: necessary.
 * Wind change: necessary to direct the "lighter-than-air device".
 * Blink: useful for short-ranged shortcuts, e.g. cross a river while enemies run after you. In the NES port, it can only be used to flee from battle, without losing Virtue Points.
 * Gate travel: useful for shortcuts to any of the eight towns.

Dungeon spells:
 * Light: more convenient than torches.
 * View: less convenient than magic gems, because of the scarcity of reagents to cast the spell; both View and the Gems are very useful in dungeons, although they can be cast on the surface, too.
 * X (Exit): useful to escape dungeons when the companions are very weakened.
 * Y (Up) & Z (Down): possibly game breakers, actually useful to circumvent a bug in the DOS port. Both omitted from the NES port.

Support spells

 * Awaken: use it strategically, e.g. after all enemy "sleep"-casters have been defeated; when facing a large number of "sleep"-casters, split your party in two: some attack the enemies, others keep waking up the asleep allies.
 * Protection: especially useful when the party is low on health points.
 * Quickness: useful to speed up a combat, thus reducing suffered damage.

NES-only spell:
 * Reflect: useful when the party is low on health points.

Disabling spells

 * Energy field: creates one of four magic fields, at the caster's choice; cast it exactly on an enemy, because some enemies can walk around the fields. If an enemy receives fatal damage from a field (poison or fire), the companions earn no experience points (the field itself deserves them...). In the NES port, a large 3x3 fire field is the only available option.
 * Blue lightning field: impassable barrier, but strong enemies can destroy it; can be cast on free tiles only;
 * Purple sleep field: inflicts "sleep" on enemies;
 * Green poison field: inflicts "poison" on enemies;
 * Red fire field: damages enemies.
 * Sleep: easy to cast and free from side effects.
 * Undead: useful against the strongest undead, i.e. phantoms and liches; still, when an undead flees, the companions gain no experience. Omitted from the NES port.
 * Negate magic: useful against powerful spellcasting enemies, especially reapers.
 * Jinx: when it affects many enemies, it becomes a great defensive-offensive spell: less damage to your party and more damage to enemies.

Attack spells

 * Magic missile, Fireball, Iceball, Kill/Destroy (sorted by power): ranged weapons are more convenient, because they have infinite ammunition and they consume no reagents.
 * Tremor: good to speed up battles against large numbers of enemies.

NES-only spells:
 * Squish: an alternative to "Tremor": it brings all enemies down to near death (actually identical to the "Necorp/Rot" spell from Ultima 3).
 * Defeat: if you focus on ranged weapons (tactically advantageous), this close-range spell becomes almost useless.