Chainmail doesn’t say how to determine which spells a Wizard may cast. Perhaps it is implied that the referee choses the spells according to the scenario. Or we might assume a Wizard may cast any spell.
If we want to determine a particular spell list for a Wizard, we could use a random method, either by drawing cards from a deck or by rolling dice. One way to get a number from 1 to 16 on dice is to roll a d8 and d6. The d8 determines a pair of numbers: 1 is 1-2, 2 3-4, and so on. Between the two numbers, choose odd or even based on the result of the d6.
I use the general term magic-user hereafter to refer to a Wizard of any power level, reserving the specific term for the more powerful of the class.
In the Valormr Campaign, Zosimos and the Elf King and Queen are seven-spell Wizards. All other magic-users have a point value of 80 (close to average by number of spells), and I dice for the power level. Spells are determined by drawing from a deck.
In addition to this randomosity, I added Chainmail’s optional Spell Complexity (33). Because the complexity was often higher than the user’s level, spells rarely took effect. A fireball, certain of effect, was more worthwhile than a spell with little chance of success. Magic-users became 80-point missile throwers.
After a brief trial, I did away with it. Spell Complexity is better used when the spell list is determined with some judgment.
To preserve some power in spell-use while incorporating Complexity, we might allow the player to choose spells of any complexity, either before play or in game. In both cases, the player judges the risk of failure.
Restricted by Complexity
To lean in the direction of later adventure games, we might throw out the chance of spell failure and restrict a magic-user to complexity levels at or below his or her power level, based on number of spells. A Seer has access to only Complexity 1 spells, for example; a Warlock, Complexity 4 and below.
Choose From a Subset or the Entire Spell List?
While the adventure game that grew out of Chainmail restricts arcane magic-users to a subset of spells—usually acquired over time and collected in a spell book, we might allow access to the entire spell list, possibly restricted by complexity as above. This carries the potential to slow play, as the player must consider more options. On the other hand, it makes magic-users a little more powerful and makes them appear more prescient, as they are more likely to have just the right spell for the situation.