In order to develop a magic system that truly captures the feel of the Lankhmar stories in play, I’ve been looking at the common threads of invoked magic in the stories. The most consistent thread is ritual. In this case, a ritual is an established or prescribed procedure performed to invoke magic.
Another commonality–and one that I think is key–is that the sorcerers, witches, etc. are tied down to a single spot, figuratively speaking. They will typically have equipment set up that they must manipulate and maintain to perform the magic. As such they cannot move away while casting, nor could they quickly set up and break down their equipment to travel between spell-casting.
Ill Met in LankhmarIn the midst of the table an alembic was working. The lamp’s flame–deep blue, this one–kept aboil in the large crystal cucurbit a dark, viscid fluid with here and there diamond glints. From out of the thick, seething stuff, strands of a darker vapor streamed upward to crowd through the cucurbit’s narrow mouth and stain–oddly, with bright scarlet–the transparent head and then, dead black now, flow down the narrow pipe from the head into a spherical crystal receiver, larger even than the cucurbit, and there curl and weave about like so many coils of living black cord–an endless, skinny, ebon serpent.
…and a little later:
Ill Met in LankhmarAbruptly the incantation peaked and broke off, like a drum struck very hard, then instantly silenced by palm and fingers outspread against the head. With a bright flash and dull explosion, cracks innumerable appeared in the cucurbit; its crystal became white and opaque, yet it did not shatter or drip. The head lifted a span, hung there, fell back. While two black nooses appeared among the coils in the receiver and suddenly narrowed until they were only two big black knots.
This suggests a mode for RPG spell-casters in Nehwon, both player character, and NPC alike. Typically RPG adaptations of the Nehwon setting simply use their own magic system and either limit the power or availability of spells in an attempt to emulate the story magic. Why not have a clean break and use this form of ritual magic?
This works well for NPCs, especially NPC villains. NPC spell-casters would have an area with their equipment set up to perform their magic rites. It would be in a place of safety for the NPC, and the PCs would have to confront the wizard on his terms. Away from this environment, he would be just an ordinary person, albeit one with a dread-inspiring reputation befitting a wizard.
This would probably not be a natural state for player-characters. Players are too used to slinging spells on the move and in combat. It would be a truer representation of a Nehwon spell-caster and offer some interesting role-playing opportunities for any player willing to try this style of a spell-casting character.
Spells can be scaled. More powerful spells would simply be more complicated, require more time, more equipment, and along with that are less mobile and carry a greater risk of failure and danger. Less powerful spells can be simpler and more mobile.
So what are the game implications?
I do not think this would work in a high-fantasy campaign as it does constrain the options of the PC. However, for a sword & sorcery campaign, the emphasis is typically on the heroes being swordsmen and rogues with the villains being the sorcerers. That being said, the player could still play a swordsman or rogue that also knows some magic thus allowing the PC to have fun in either situation.