I'll try to explain how magic works in AD&D, which is the rule set used in the original Icewind Dale. Icewind Dale 2 uses the 3rd edition D&D ruleset which has similar rules for magic, but not exactly the same.
There are two kinds of spells: arcane spells and priest spells. Arcane spells are cast by mages, while priest spells are cast by clerics, druids, paladins and rangers. There are two separate spell books and characters can only cast the spells for their class (a dual-class mage/cleric or course can cast both).
The manual has a number of tables in the appendix and one of those is the table of mage spells for mages per level. A level 1 mage has one level 1 spell. A level 2 mage has two level one spells. A level 3 mage has two level 1 spells and one level 2 spell. On level 4 that's three level 1 spells and two level 2 spells. The list goes on. If your mage is a specialist mage (like necromancer) you get one extra slot per spell level, but you can't cast spells from the opposite school (necromancers can't cast illusion spells). Mages with high intelligence are able to learn (learn, not cast) more spells per level. Finally, there is a bonus in spell slots for high wisdom for clerics and druids, how much exactly is in another table.
For other classes it's similar, except they have their own tables. Bonus priest spell slots are granted for high wisdom though, not for high intelligence.
When you open your spell book there will be two pages for each level. The left page has the slots and the right pages has the known spells. To prepare a spell click it on the right page and it will appear in a slot on the left page. After resting for eight hours your caster will be able to cast any spell that has been prepared in that way. To be able to cast a spell multiple times fill multiple slots with it. After a spell has been cast it will be faded out in the spell book. The spell is still prepared, but you will need to first before you can use it again. To un-prepare a spell klick its slot and the slot will be freed to fill with another spell.
How do you learn new spells? Priest spells are all all learned once you become able to cast spells on that level. So once your cleric reaches level 3 he or she learns all the level 2 spells (of course they still only have one level 2 slot). Mages must learn spells from mage scrolls. When you find a scroll open your inventory, right-click it and click "write magic". That will copy the spell into your spell book. You can even learn spells from levels you can't cast yet, but you won't be able to use them until you get at least one slot.
Finally, you can cast spells from scrolls directly, this goes for both mage and priest spells. There is no limit, it doesn't use any slots and I think you can even cast spells you don't have the level for. However, after the spell has been cast the scroll is destroyed, so each scroll has only one charge.
TL;DR Being able to cast one spell per day is normal. Create a specialist mage for an extra spell and give your mage high intelligence for bonus spells. Still, for the first few levels your mage will just be sitting in the back row after unloading his or her spells. Once mages learn Fireball (level 3 spell) they become your main force. Until then use them as supporting fighters. Debuff spells or spells like Sleep or Charm Person are good choices
Post edited August 29, 2014 by HiPhish
