Petition Roll (clerics)
2 or less – Abandoned (specific petition unavailable, any abjuration ends, cumulative -1)
3, 4, 5 – Spurned (Spell goes off at end of turn, cannot cast spell again cumulative -1)
6, 7, 8 – Ignored (Spell goes off at end of turn, may try again next turn)
9, 10, 11 – Answered (standard success, spell goes off immediately)
12 + – Rewarded (double effect, demons or undead destroyed, etc)
Sorcery Roll (magic-users)
2 or less – Catastrophe (chaos surge/mutation/backfire, spell lost, cumulative -1)
3, 4, 5 – Miscast (chaos leak) spell goes off at end of round. Cannot cast again.
6, 7, 8 – Spell goes off @ end of round, may be interrupted, Can cast again
9, 10, 11 – Success, spell goes off immediately
12 or more – Puissant success (extended duration, full damage, or something similar)
Caster gets 2 d6’s plus a number of d6’s equal to level + stat bonus (dice being rolled for spell must be less than spell level with the minimum dice rolled being 2d6). You add your casting stat bonus and your level to the roll and subtract armor worn. They may roll as many as they wish for spells. On ones, they lose the dice. Or possibly on any roll lower than the spell level, they lose the dice. (I.e. a second level spell would lose dice on ones or twos.)
Cumulative penalties go away and spells may be re-prepared after characters return to civilization and rest for a night, along with appropriate prayer or study.
The differences between cleric petitions and sorcery are as follows.
need not be prepared but is limited to the powers granted by a particular order or patron.
More ritualistic, and with the exception of a few limited combat effects (such as turn undead or hold person) requires at least an exploration turn (and often a full day) to attempt.
requires preparation but set of effects to choose from is limited only by spells known
Sorcery is also more directly potent and more dangerous (potentially causing chaos leaks, mutations, backfires, and all kinds of nastiness)
Example of Play
So you’re a second level caster with a 16 intelligence. You have 2 + 2 + 2, six dice.
This is B/X so you have magic missile and sleep memorized.
You cast magic missile during a fight. You roll 2d6 and get a 1 and a 6. The spell goes off at the end of the round and you lose one die from your pool. You can still cast magic missile again.
The next door you open and you get charged by an ogre. It’s really important to get the spell off early, so you roll 4d6 (of your remaining pool of 5). You roll a 1, 4, 5, 3, for 13 and lose another die from your pool. The spell goes off at the start of the round. You lose another die, leaving 4
Later you are in an extended fight with goblins. It lasts 8 rounds. You cast magic missile from the back each round using 2d6.
2,6, for 8 goes off at end of round.
1,2 for 3 goes off at end of round and you lose the spell and 1 die. Your pool now has 3d6 in it, and you can only cast sleep.
2,3, for 5 to cast sleep, and then you lose sleep and you are out of spells.
This way, you have the xd6 roll, you have arcane stress (die loss) and you are much more limited/risky with higher level spells (Sure you get more dice on higher level spells, but you lose them when you roll 1’s and 2’s). Light armor could increase your ‘lose your die’ value by 1, medium by 2 and heavy by 3. You would of course get all your dice and spells back after your nights rest. P.S. I rolled all the above using a dice roller.