The Revolution of Sigmar
Confirming a Critical Fumble: When you roll a natural 1 (the die shows a result of ‘1’), your attack automatically misses the target and threatens a critical fumble. In order to confirm the critical fumble, roll a second attack roll with the same modifiers as the attack that threatened the critical fumble. The DC to confirm a critical fumble is equal to your flat-footed AC. If your attack was a touch attack, your critical fumble is also resolved as a touch attack, removing your armor and natural armor bonuses to AC as accordingly. If this second attack roll beats your AC, the attack is a critical fumble.
Critical Fumbles: When you critically fumble, draw a card from the Critical Fumble deck. The effects of the card are immediately applied against you, based on the weapon used to critically fumble (melee, ranged, natural, or magic). A natural attack is any attack made with a non-manufactured weapon, such as an unarmed attack, a slam attack, or claw attacks. Unless specifically stated otherwise, the DC against the effects of a Critical Fumble card is equal to the attack roll used to confirm the critical fumble. If you are immune to the card’s effects, you instead take damage as if you had attacked yourself, using all of your normal modifiers to damage done. If you cannot apply a card’s effects and you rolled a natural 20 on the roll to confirm a critical fumble, roll to confirm the critical hit against yourself and follow the rules for critical hits (listed below) accordingly.
Exotic Effects and Critical Fumbles: Psionic powers are treated as spells for the purpose of critical fumbles. Supernatural abilities and extraordinary abilities are treated as natural attacks for the purpose of critical fumbles.
Saving Throws and Critical Fumbles: When you roll a natural 1 against a saving throw, you automatically fail your saving throw and threaten a critical fumble. In order to confirm the critical fumble, roll a second saving throw with the same modifiers as the saving throw that threatened the critical fumble. The DC to confirm a critical fumble caused by a saving throw is equal to the DC of the save that you rolled a natural 1 against. If you fail this second saving throw, the save is a critical fumble.
Weapon Focus and Critical Fumbles: When you critically fumble with a weapon that you possess the Weapon Focus feat with, you can draw 1 additional card and choose which card to apply to yourself as part of the critical fumble. The card not chosen is not applied and is discarded.