I'm working on a new style of magic (tentatively: Psychic Magic), one that uses a radically different casting system, and I'd like some advice.
Rather than using spell levels as a flat rate, the caster has "spell points" that stack with hit points; spell points are gained like hit points, once per level. A class with a d6 hit die and a d6 spell die would then gain an average of 7 spell points per level. I'm working on a formula to balance spell casting; the current model uses (spell level)2, which isn't horrible, except for level 1 spells. No more than 4 build points can go towards hit dice and spell dice; spell dice build progression is as follows:
0: no spell points; 1: spell points = hit points; 2: spell points = 1d4 + hit points; 3: spell points = 1d6 + hit points; 4: spell points = 1d8 + hit points
While spell points are above hit points, casting simply uses spell points. However, once spell points equal hit points, casting does 1 point of nonlethal damage per 1 point used - that is, if a caster have 20 spell points and 10 hit points, casting a 3rd level spell (9 sp) doesn't hurt him at all. However, casting a 4th level spell (16 sp) does 6 points of non-lethal damage to the caster. Casting a spell that would drop you below 0 hp is not allowed, nor is casting a spell that costs more spell points than you have available. That has two effects - spending all your spell points will knock you out and force a roll on the mortal wounds table, and getting damaged will affect how many spells you can cast in a day. Healing damage (non-lethal or otherwise) will restore the ability to cast those spell points, if available, but will grant no new spell points.
This has the odd effect of allowing a lot more spells to be cast (a level 14 d6+d6 caster could cast, if at average health, 98 first-level spells), higher-level spells to be cast (the same caster could cast 2 7th level spells), but also a lot fewer spells (the same caster could cast only 3 5th level spells, 1 4th level spell, 1 2nd level spell, and 3 1st level spells in a single day).
No spellbook is required; the full list of spells (5-10 per level, similar to divine magic) is available, as long as spell points can be spent, and is known automatically. I haven't worked out ritual magic yet; there may not be any for this class. This is mental magic, so it'll be heavy on death (psychic blasts), enchantment, movement (telekinesis), and illusion, but light on walls and summoning (if any). Casters will not be able to research spells, scribe scrolls, or create potions or crossbreeds, though will be able to create items usable only by psychics (psychic foci), and grant un-life.
The only problem I'm having is the level 1 spells. Fully maxed spell points can only cast 4 7th level spells a day, plus a small handful of 1-3 level spells... but even an average caster with only a single build-point could cast 35 1st level spells a day! My only idea on how to fix that is to make the first level spells super weak, largely utility, and the (single) damage-dealing spell being attack-throw based, and/or avoided with saves.