The next couple posts I'm working on present a few options for spellcasters, arcane and divine, in the classic D&D games. Before I start, I'll touch on a few points about the actual rules for spell casting and how I use them. Future posts will assume familiarity with my house rules, but should be easy enough to tweak to your own, or back to the rules as written.
According to the rules, Magic Users, Elves and Wiccas must study and select the spells they plan to cast before each day of adventuring. Clerics, Druids and Shamans, on the other hand, select their spells from those available when they want to cast them.
First off, I dislike the different treatment of arcane and divine magic. One system should apply to both types.
I tweak things to apply the same rules to all spell casting classes. Any spell caster has the following option:
1: Spells may be studied and selected as per the rules for MUs and Elves and then cast normally during play
2: Spells may be cast "on the fly" as needed during play, but an initiative penalty of 1 per level of the spell being cast is applied to reflect the added time needed to recall a spell that has not been thoroughly prepped.
The two options may also be mixed. A character with two first level spells allowed for the day may choose to fully memorize one, and save the other one for on the fly casting as needed.
Like MUs and Elves, I require Clerics (and druids and shamans) to learn and keep a record of spells available to them, generally in a prayerbook, but this is not required if the character comes from a culture or religion that has no written tradition. The player must keep a list of the spells the character "knows" either way though.
All spellcasters (excepting clerics, druids or shamans (and possibly wiccas, DM's discretion) from oral traditions, must keep a written record of the spells they know. Arcane casters call these spellbooks, Divine casters call them prayerbooks, though the term book is somewhat general, and the documents may actually consist of scrolls, loose sheets of parchment, etc.
Spellbooks cost 10 gp + 1gp per page. The 10gp base price is for binding and covers, and may be waived if the caster wants to use scrolls or loose, unbound sheets, DM's discretion. There is theoretically no limit to the number of pages in a book, but 50 to 100 pages is the norm for spellbooks that are portable enough for packing for an adventure.
Spellbook quality ink costs 1gp per vial, and each vial has enough ink for 10 pages of writing. Quills are available almost anywhere for 1cp.
Each spell takes up 1 page per spell level.
Learning New Spells:
Except for initial spells at level 1, a character must make an ability check on the relevant ability for his class (INT for MU, Elf, Wicca; WIS for Cleric, Druid, Shaman) to understand and learn a new spell he wants to add to his spellbook. If this check fails, the caster must wait until earning another experience level before attempting to learn the spell from that source again. This means that if Zoe the MU finds a scroll of ESP and wants to learn that spell, she must make an INT check before adding it to her spellbook. She fails the first attempt, and can't puzzle out the workings of the spell, although she could still use the scroll as normal. Instead she decides to hold onto it and try and learn it again after gaining her next level. If, on the other hand, she finds a different source of the ESP spell, from the spellbook of an NPC MU for example, she can attempt to learn the spell again immediately, studying the new source instead of the old.