Class Combinations

One of the biggest points of confusion in the OD&D is how multiclassing works (otherwise known as the "oh my god, not elves again" problem). Elves are said to switch between Fighting-Men and Magic-Users, "not during the course of a single game", but "gain the benefits of both classes and may use both weaponry and spells" (Vol. 1, p. 8). Other races are "not recommended" for changing classes, but rules are given if so allowed (men require 16 prime requisite: Vol. 1, p. 10). Furthermore, the exact mechanical effects of having two classes are not described anywhere. Here's my best attempt at resolving those issues.

Classes
In my campaign, allowed classes are: Fighter, Cleric, Wizard, and Thief.

The Thief class is taken from Supplement I: Greyhawk, as follows. All thief skills are checked at d20 + level >= 20 for success. Hear Noise is as per book; Climbing fails only on a "1" on d6 through 5th level. Hit dice follow the magic-user progression.

Races
Allowed races are as follows: Human, Dwarf, Elf and Hobbit (halfling). The classes allowed to each are shown below, with level limits in parentheses.

Human: Any class (unlimited).
Dwarf: Fighter (6th), Cleric (7th), Thief (unlimited).
Elf: Fighter (4th), Cleric (6th), Wizard (8th), Thief (unlimited).
Hobbit: Fighter (4th), Thief (unlimited).

Adding Classes
Every character begins with a single class of their choice. Most characters can add a second permitted class of their choosing at the end of any adventure. (Exception: Humans must have an ability score of 16 or more in any class they are adding.) Each adventure's XP must be allocated towards a single class, possibly a new one in order to add to it.

The level limits shown above assume a character with two classes. If a character maintains only a single class, then they can add +2 levels to any limit shown above. For each class added beyond two, -2 levels are deducted from any limits shown.

A character with more than one class can use all of the abilities from any class (weapons, armor, spells, skills, etc.). They use only the best entry for Hit Dice, Attacks, and Saves. Fighter/Wizards may cast spells in leather or chain mail, but not plate. Thief skills are restricted to leather armor only.

Finally, the DM may decide to start a campaign with characters above 1st level. If this is done, a starting XP value should be awarded which can be allocated in units of 1,000 at a time. (For example, a 3rd-level campaign might award 5,000 XP to begin with.)


Design Notes: OD&D
As usual, I've tried to hew as closely to OD&D as possible, using supplements for themed inspiration to fill in the gaps. The level limits for fighters and wizards are as shown in OD&D -- and so is the ability restriction on men. The language about switching classes (but not within one game) has been interpreted as allocating XP to only one class per adventure.

Level limits for clerics and thieves are taken from Supplement I: Greyhawk. The +2 level bonus for keeping a single class is in flavor with the increased level limits shown there (in that case, for having high ability scores). Likewise, the -2 penalty is in line with the reduction in magic-use for elves with three classes in Greyhawk (the only such example).

Using only the maximal values for Hit Dice, Attacks, and Saves is necessary because adding new class levels is so cheap compared to the XP gained by already-advanced characters; that is, there really must be very little mechanical benefit or the XP-cheapness will create a very broken mechanic. As a strategy suggestion, it may be a good idea for characters to start as Fighters to increase survival odds, and then add spellcasting classes later on.

As a side note, I'm very happy with the restriction on humans multiclassing, because it solves the question of "why years of training for your starting wizard, but then a fighter is able to add it whenever he wants?" The high ability score precisely represents the extraordinary aptitude (and possibly prior training) needed for just such an addition.

Design Notes: 3E D&D
At this point, I must also take the time to highly commend the system used by 3E for classes and multiclassing. Trying to iron out the jagged parts of OD&D/AD&D multiclassing has made me appreciate that aspect of 3E even more. It was truly a stroke of genius to collapse the XP table to a single chart, and allow all multiclassing as a purely additive mechanic. I never would have thought of that, and it cleans up the system to a remarkable agree.

With this fine print: As long as we restrict the system to just 4 classes (Fighter, Cleric, Wizard, Thief), then the 3E class system is absolutely my favorite and I'd love to use that in my game. However, if there are dozens of classes and prestige classes, and PC constructions start having 7-8 class notations each with 1-3 levels (like a Sws3/Ftr2/Mnk6/Swd3/Rog3/Nin2, from just the first example I could find on the Wizards.com forums), then my eyes glaze over and I want to play a different game. And then additionally with 3E, you're stuck with all the complicated monster statistics and reduced fiddly spell powers, and it's not nearly so much fun to think about anymore.