Recently, I've been working on a sorcerer class for Castles & Crusades. I want to present him as a spontaneous caster who cannot always handle to primal energies he's channeling. Therefore, I depicted him as more of a Wild Mage--for starters, he needs to roll when casting. On a natural 1-2, something unexpected happens, and it generally ain't good, though the seasoned Sorcerer will learn how to turn some negatives into positives. Here's the quick n' dirty chart I made up:
Sorcerer Spell Failure Table (Roll 1d20)
(Note: All particulars at GM discretion)
1) Spell forgotten; relearned in d8 hours.
2) Lose all but 0-level spells for 1d4 rounds.
3) All in 30’ radius take 1d4 fire damage.
4) Caster glows brightly for 2d4 rounds.
5) Caster blinded 2d6 rounds.
6) Spell casts at half effect, caster asleep d10 min.
7) 50’ radius filled with black smoke 1d6 minutes.
8) All in 30’ radius take 1d6 cold damage.
9) Spell does opposite of normal effect.
10) Polymorph cast on self instead. Goblin form.
11) Spell forgotten; relearned in d6 weeks.
12) Lose all but 0-level spells for 1d4 days.
13) All food and water spoils within 25’ radius.
14) Seismic event; STR check to stay upright.
15) All in 30’ radius take 1d6 lightning damage.
16) Animal summoned; caster has no control.
17) Caster becomes elemental being 1d4 rds.
18) Random spell of +d4 levels cast.
19) Hungry infernal being summoned; stays d4 rds.
20) Spell forgotten; relearned in d6 months.
I will likely eventually expand this to a d100 chart, but I think it works well enough as a starting point. The finished version, however, must contain a grue.