A multiclass character gets all the class features of all his or her classes but must also suffer the consequences of the special restrictions of all his or her classes. (Exception: A character who acquires the barbarian class does not become illiterate.)
Spells
The character gains spells from all of his or her spellcasting classes and keeps a separate spell list for each class. If a spell’s effect is based on the class level of the caster, the player must keep track of which class’s spell list the character is casting the spell from.
Rogues are proficient with all simple weapons, plus the hand crossbow, rapier, sap, shortbow, and short sword. Rogues are proficient with light armor, but not with shields.
Wizards are proficient with the club, dagger, heavy crossbow, light crossbow, and quarterstaff, but not with any type of armor or shield. Armor of any type interferes with a wizard’s movements, which can cause her spells with somatic components to fail.
Druids are proficient with the following weapons: club, dagger, dart, quarterstaff, scimitar, sickle, shortspear, sling, and spear. They are also proficient with all natural attacks (claw, bite, and so forth) of any form they assume with wild shape.
Druids are proficient with light and medium armor but are prohibited from wearing metal armor; thus, they may wear only padded, leather, or hide armor. (A druid may also wear wooden armor that has been altered by the ironwood spell so that it functions as though it were steel. See the ironwood spell description) Druids are proficient with shields (except tower shields) but must use only wooden ones.
A druid who wears prohibited armor or carries a prohibited shield is unable to cast druid spells or use any of her supernatural or spell-like class abilities while doing so and for 24 hours thereafter.
Arcane Spell Failure
Armor interferes with the gestures that a spellcaster must make to cast an arcane spell that has a somatic component. Arcane spellcasters face the possibility of arcane spell failure if they’re wearing armor. Bards can wear light armor without incurring any arcane spell failure chance for their bard spells.
Casting an Arcane Spell in Armor
A character who casts an arcane spell while wearing armor must usually make an arcane spell failure roll. The number in the Arcane Spell Failure Chance column on Table: Armor and Shields is the chance that the spell fails and is ruined. If the spell lacks a somatic component, however, it can be cast with no chance of arcane spell failure.
Shields
If a character is wearing armor and using a shield, add the two numbers together to get a single arcane spell failure chance.
An armor check penalty number is the penalty that applies to Balance, Climb, Escape Artist, Hide, Jump, Move Silently, Sleight of Hand, and Tumble checks by a character wearing a certain kind of armor. Double the normal armor check penalty is applied to Swim checks.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.