Armour and magic

Leather, chain and plate have no inherent spellcasting penalty. Wearing armour or carrying a shield does not by itself increase spell costs, slow casting or weaken spells. Bonuses on the equipment can affect magic, and its weight counts toward your carrying load.

Your class can forbid armour types, shields or materials. Metal mail pieces still count as chain for armour-type restrictions; metal brigandine pieces count as leather. Material restrictions apply as well.

Armour rating protects against physical blows. For protection against hostile magic, look for resistance bonuses, socket gems and protective spells.