(I’m swiping the “combining classes” rule from the Basic Fantasy RPG for my Labyrinth Lord campaigns. I think it’s a lot easier than the AD&D/AEC system.)
The following replaces the AEC Multiclassing rules (p.24):
At the referee’s option, characters may advance simultaneously in two classes. The character must meet all requirements of the chosen classes. The multiclass character gains all special abilities of both classes, and uses the best hit points, attack values, and saving throws of each. However, they must gain experience equal to the combined requirements of both base classes to advance in level, and their maximum level is limited to the lowest of the two classes chosen.
Traditionally, humans are not allowed to multiclass, but this is permitted in my home games. (Some humans may also be permitted to switch classes during play.) Demihuman race-classes may not multiclass.
Subclasses may not multiclass with other classes of the same type (so no fighter/rangers or magic-user/illusionists). Due to their beliefs, lawful clerics (including subclasses) cannot multiclass as magic-users or thieves, and paladins cannot multiclass at all.
Multiclass characters sometimes gain class abilities that would otherwise conflict. Notes on specific class combinations follow:
- Multiclass clerics (and cleric subclasses) may use any armour or weapons appropriate for the other class.
- Multiclass fighters (and fighter subclasses) can combine their abilities freely with any other class.
- Multiclass magic-users (and magic-user subclasses) may cast spells normally while using armour or weapons appropriate for the other class.
- Multiclass thieves (and thief subclasses) may use any armour or weapons appropriate for the other class. However, the thief armour restriction still applies so that if a multiclassed thief wears armour heavier than studded leather or uses a shield, thief skills may not be employed.
Example: Gimp Froodle is a a gnome fighter/illusionist. He uses the best hit points, attack values, and saving throws from his two base classes. He may wield weapons as a fighter and can cast illusionist spells while wearing armour. Gimp requires 4286 XP to advance to 2nd level, and is limited in advancement to 6th level.