Spontaneous Casting: Clerics no longer prepare spells. They can spontaneously cast any spell they know, which “spends” the corresponding spell slot. As usual, sleep and meditation is required to recover spent spell slots.
Casting: Elves are innately sorcerous. Instead of using Spell-Orbs (see Magic-User), spells simply emanate out of an Elf's hand, though they share the Magic-User's spell list.
Mind-Palaces: Instead of a spellbook, Elves carve their spells into their personal Mind-Palace, which exists in the plane of dreams.
Transcribing a new spell into their Mind-Palace requires a long and deep trance and the use of special incense and potions. In terms of time and gold cost, this is the same as for Magic-Users. However, unlike a spellbook, the Mind-Palace cannot be physically stolen or destroyed (although astral travel into the plane of dreams may enable one to vandalize an Elf’s mind palace, or steal spell formulae). An Elf’s Mind-Palace starts with only the Read Magic spell.
Preparing & Learning: Elves still prepare spells into slots, which is done during their nightly sleep/trance. Each time they gain a level, an Elf learns a new spell of a level of their choice and adds it to their Mind-Palace at no gold cost (though the time requirement still applies).
Preparing: When Magic-Users prepare spells (which requires access to their spellbook), they create a one-use physical object for each prepared spell called a Spell-Orb.
Appearance: Assume a Spell-Orb takes up roughly one "slot" of inventory, or about the same space as a flask of oil. Most Spell-Orbs appear as glass balls with energies swirling inside them. However, they may also be any other sufficiently sized fragile and obviously mystical object: a charm made of sticks and bones, an unstable alchemical concoction in a bottle, or a latticework of herbs and crustacean legs joined with the mixed saliva of birds and the Magic-User. A Spell-Orb may be set into the tip of a staff for convenience.
(The reason Magic-Users often wear long robes is to conceal their Spell-Orbs within the myriad folds and secret pockets, in order to prevent assailants from snatching or destroying them.)
Casting: Using the Spell-Orb requires gesturing with it, which then triggers the spell and destroys the orb. Ranged spells require the orb to be thrown, though they cannot miss; they orbs transform mid-air into magic missiles, fireballs and so on, functioning just the same as any other spellcasting method.
Other characters may also use Spell-Orbs created by a Magic-User. Characters who are not Magic-Users, or Magic-Users of an insufficient level to cast the spell, can attempt to use them with a risk of failure. When you make such an attempt, roll your Arcana skill (1+INT in 6, Magic-Users have +1) with a penalty equal to the spell’s level. Example: if your Arcana skill is 4 and you use a 2nd level spell, you have a 2-in-6 chance of succeeding.
If the Arcana attempt fails with a roll of 6 on the die, the spell is a misfire: it is triggered but with its target or effect reversed (as deemed appropriate by the Referee). If it fails on any other number, the spell is not triggered and the Spell-Orb remains unused. A character who has failed to trigger a specific orb may not attempt to use that orb again, though it is still usable by others. Thrown Spell-Orbs (i.e. ranged spells) that fail to trigger merely fall onto the ground, but when hitting a hard surface have a 1-in-6 chance to shatter. When a fallen orb shatters, it triggers the spell, targeting the space it landed in. Fallen spell orbs can also be shattered by missile attacks (AC 17 to hit).
Unused Spell-Orbs harmlessly disappear out of existence when the Magic-User recovers their spell slots. When the Magic-User dies, each of their active spell orbs has a 4-in-6 chance of dissipating harmlessly, and a 1-in-6 chance of exploding and triggering the spell, otherwise persisting and remaining usable by others.
Gaining new spells: Spellbooks work as before: each time they gain a level, a Magic-User learns a new spell of a level of their choice and adds it to their spellbook at no gold cost (though the time requirement still applies).
(Note that only Magic-Users use spellbooks and spell orbs, though all casters still use the system of spell slots.)
The physicality of orbs will help players unfamiliar with Vancian casting grasp the meaning of spell slots. In Vance’s stories, spells are living things that inhabit a wizard’s head through his concentration and discomfort. Now, they will be concrete things the character can hold. Also, this will make inventory management a factor for Magic-Users (particularly suited to slot-based inventory systems, and those with rules for item breakage). Allowing other characters to use orbs opens up new possibilities, but at a risk. As for shattering orbs, I’ve always liked how in Nethack et al. burned scrolls can explode, broken potions still apply their effects, and so on. It really ties magic into the environment, a real part of the world. (And, honestly, I kind of want to see someone try to jam a fireball orb down a white dragon's gullet.) Also, spell orbs once again harken back to certain concepts in Dave Arneson's early games, though I do not know how the mechanics there exactly worked. If you have good information on Arnesonian spell balls, please let me know.
Many systems try to take out the spellcasting system from D&D and replace it with something else, like spell points. None so far have produced better results in play than the original system.
I currently have no interest in redoing the entire spell system, or writing new spell lists, or most importantly, breaking compatibility with existing TSR & OSR materials. However “slots vs. spell points” is not the only parameter that can be modified in the spell system. There are at least the following parameters, off the top of my head:
- Casting spells - the actions required to activate a spell, and any restrictions to doing so such as “no armour”, and any side effects of these actions (magical mishaps, etc.)
- Preparing spells - when and how a character chooses the spells available for the adventure, or if they have all the spells they know available (spontaneous casting)
- Learning spells - whether a character knows all spells on their list, or knows a subset of it, and whether there is a maximum on the size of the known subset
- Spell resources - what is spent to use spells: spell slots and spell levels, spell points, HP drain, increasing risks, etc.
It appears to me that the other parameters - how to cast spells, how to prepare spells, and how to learn spells - are a much more fruitful area for modification. Changes to them have a much smaller interface with the rest of the rulebook - although they may still have far-reaching balance consequences during play (such as allowing Magic-Users to cast spontaneously).
With small changes like these to how your spellcasters learn, copy, prepare and cast spells, you can give them unique flavour without invalidating existing spell lists and compatibility with modules. The possibilities are endless. Imagine, for example, a druid’s spell slots each taking the form of an animal spirit when not prepared, or an elf who can only channel spells through weapon attacks, or...