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MAD stands for Multiple Ability score Dependent. It happens when a 3.5e character build relies on several different ability scores to be effective. Common base classes, multi-classed characters, and many PrCs suffer from this. To test if your proposed character suffers from MAD, ask yourself this: "Given the standard array of ability scores (15,14,13,12,10,8) where would I put stuff?" If you find yourself saying, "Well, crud, I need more ability scores to cover my bases!" then you suffer from MAD.
Common Classes that suffer from MAD:
Monk - need Str (to hit/damage), Dex (no armor, also for several skills), Wis (for AC and other monk abilities), Con (Monks get d8 hit die and are often in combat), and a little Int (b/c the monk has a good bit of skills).
Paladin - Str (to hit/damage), Wis (spells), Cha (several abilities), Con (more HP, in combat)
Ranger - Str (to hit/damage), Dex (bows, 2weap fighting feats, skills, light armor), Con (d8hit die), Wis (spells), Int (lots of skills), Cha (calm animal and such).
To a lesser extent, Bards and Duskblades, for many the same reasons as above.
Multi-class characters often suffer from MAD, most specifically the "Gish" (Fighter-Wiz) and anything trying to cross strength fighting ability with Dexterity based skills.
Another problem that arises from MAD is whether to go with the Dex-based fighter or the Str-based. Dex-based usually get weapon finesse and light armor, but suffer from lack of bonus damage output; they also often use dual wielding, resulting in low AC. Str-based fighters usually go with heavy armor, which cuts down on their spell-casting ability and Dex-based skill usage.
This has been written by Addison Plaisance at firstname.lastname@example.org. Nothing is copywrited information from any other source.