Editing System grab-bags:Dice-based (section)

===Botch dice===

If the ”failure number” is rolled, the failure is not automatic. Instead, a variable number of dice are rolled - the worse the circumstances, the more dice. If any of them turns up the ”failure number”, the task fails. The more failure numbers, the worse the failure.

Example: On an attribute + D10 roll, the player rolls a 0, indicating a possible failure. The circumstances give her three botch dice, so she rolls three D10s, which come up (4, 3, 0), confirming the critical failure (though only a mild one).
Game examples: Ars Magica