Vyvyan Basterd
Adventurer
A friend of mine ran his AD&D campaign out of the back of his hobby shop back in the late 80's. A player of his tried to describe the house rules for casting spells to me. All castings were based on a percentile roll to dtermine effectiveness, with zero indicating minimum effect and 100 indicating maximum effect. Examples given were: A roll of 100 when casting Fireball would generate a nuclear explosion that would most likely kill the caster and plunge the campaign world into a world-ending catastrophy. A roll of 100 when casting Dispel Magic would destroy all magic in the entire world (maybe multiverse, never bothered asking), causing magical creatures, such as dragons, to die instantly...every one out of one hundred castings of a spell by any caster, PC or NPC!