This is Part 3 of a series to convert Moldvay Basic classes to Chimera. For convenience, you can use the Race as Class tag to view every article in the series, including the first instalment that contains the ground rules for conversion. This week’s entry: The B/X magic-user.
UPDATE (7/20/11): Clarified the magic-user Sperks and the Magically Attuned capabilities.
Moldvay describes magic-users as “humans who, through study and practice, have learned how to cast magic spells.” (B10) They cannot wear armour, their only weapon is the dagger, and their hit dice is a mere d4. On the upside, they can cast spells, use certain magic-items, and, at higher levels, create new spells and magic items.
I’ll be honest—I have some issues with the magic-user class, mostly because the XP requirements are widely disproportionate to the class’ abilities. 
The other problem is that the magic-user carries a lot of baggage, namely the Vancian model, which is more about the mechanics of spell-casting than a rationale for how magic works in the campaign. I’ve heard many Vance apologists defend the system with eloquence, and I can see their points—it’s just that I've never really cottoned to it. 
And, while great stress is applied in the rules to a magic-user’s scholarly pursuits, it’s really only when you start interpreting spell acquisition or using scrolls that these traits (and the magic-user’s intelligence) actually start to have in-game consequences. Otherwise, the class is pretty much an n-shot magic item.
But, my castigation aside, the magic-user is implied as the scholar of any party, capable not only of understanding and manipulating arcane magical forces, but being the “brains” of any operation. It’s the magic-user who translates forgotten runes, identifies strange objects, reveals the backstory of supernatural encounters, and (it is supposed) helps the party work smarter instead of harder.
Magic-users are humans who understand and use the magical energies of the setting to produce spells and invoke enchanted items. While generally immersed in study and research, adventuring magic-users invariably seek out magical knowledge, spells, and artefacts. Unused to combat, magic-users do not wear armour, nor are they proficient with any but the smallest weapons.
Advancement Cost 
Move Rate: 12”±1d6
Wound Limit: 1d4
Abilities: Academics, Observe, Wield
Perks: Magically Attuned (see below), Spells (select 4 schools at start of play, with 1 random spell per school) 
Alchemist: Improve Wield ARs when creating potions by level 
Artificer: Improve Wield ARs when creating powered items by level 
Magic Resistance: Improve Resistance vs. Powers by level
Scribe: Improve Wield ARs when transferring spells from scroll to spellbook by level 
Somatics: Able to wear armour, but at a penalty to Wield rolls (Light armour, AR -1; Medium armour, AR -2; Heavy armour, AR -4)
Spells: Access to additional power school
Strong Mojo: Improve Wield rolls with a specific power school by level
Seems like the magic-user should have some “automagical” abilities: basic arcane skills that don’t require actual spells to achieve. Let’s try these:
Cantrip: Allows the magic-user to create a minor magical effect with a successful Wield roll, up to once per level each day, with the following restrictions: The effect cannot cause more than 1 point of damage or 1d4 points of Fatigue, it must have instant duration, it cannot directly affect anything with an Encumbrance value greater than zero (0).
Detect Magic: A successful Wield roll detects magical auras within 1” per level; a Critical Success reveals the school of the power detected.
Mana: Roll 1d8 for mana
Read Magic: A successful Academics roll translates scripts written in arcane, lost, or forgotten languages; this skill is also required to understand a scroll before using it or scribing a spell into a spellbook.
Note that failed Wield rolls against the above do not impose Fatigue penalties.
You know the drill: how well does this conversion “work?” As before, I’ll probably use this (or a variant thereof) to model the mages of Swords of Telm. Naturally, I’m curious to hear what you think.
There’s some math to support this in my Building the Perfect Class essay from 2003. Suffice to say it’s a game balance thing, which probably made sense in the Chainmail days, when a single Wizard could clear whole lines of Fighting Men off the field, but in the B/X context, I think it’s more appropriate to beef up the class and make it worthy of the high XP cost.
I sense that the writers of the Dungeons & Dragons cartoon shared this sentiment: Presto didn’t even come close to following the canonical rules for being a magic-user—he was essentially a Normal Man with a hat of wonder. Bogus.
My target AdCost is 10 (2,500XP / 250 = 10).
Upon learning a power school, magic-users get one random power from it straight away, but they have to learn the rest individually (CB/9). This is different from clerics, who can access every power in a school as soon as they learn it.
This makes more sense when you understand the guidelines for creating powered items, which are, sadly for you, secrets known only to me. Actually, these are included in Chimera 2.0, but need to be updated, and I'll share that revision via a separate post anon.
This assumes that magic-users augment their spellbooks via scrolls, in the time-honoured B/X tradition; again, a topic better covered in a separate post.
Moldvay, Tom, ed. Dungeons & Dragons Basic Rulebook. Lake Geneva: TSR Hobbies, Inc. 1981.
Smale, Erin. Chimera Basic. Atlantic Highlands: The Welsh Piper. 2011.