The Revolution of Sigmar
Confirming a Critical Hit: When you roll a natural 20 (the die shows a result of ‘20’), your attack automatically hits the target and threatens a critical hit. In order to confirm the critical hit, roll a second attack roll with the same modifiers as the attack that threatened the critical hit. If the attack was made against the creature’s touch AC or flat-footed AC, the roll to confirm the critical hit is as well. The DC to confirm a critical hit is equal to the AC of the creature that you are attempting to confirm the critical hit against. If this second attack roll beats the creature’s AC, the attack is a critical hit.
Critical Hits: When you critically hit a creature, draw a number of cards from the Critical Hit deck equal to your weapon’s critical multiplier minus one. (Most weapons have a critical multiplier of x2, allowing their wielders to draw 1 Critical Hit card on a critical hit.) The effects of the card are immediately applied against the critically hit creature, based on the type of damage done to the creature (bludgeoning, piercing, slashing, or magical). Unless specifically stated otherwise, the DC against the effects of a Critical Hit card is equal to the attack roll used to confirm the critical hit. Creatures that are immune to the card’s effects instead take increased damage; multiply the damage die (but not any modifiers to weapon damage rolls) by an amount equal to the weapon’s critical multiplier.
“Bank” A Critical Hit: Whenever you would critically hit a creature, you can instead choose to draw a card without using its effects. You must make this decision before looking at the card’s effect. If you choose to bank the critical hit card, you can later trade it in during the same campaign session it was banked in order to prevent a critical fumble (see above), representing your good fortune.
Exotic Effects and Critical Hits: Psionic powers are treated as spells for the purpose of critical hits. Supernatural abilities and extraordinary are treated as natural attacks for the purpose of critical hits.
Saving Throws and Natural 20s: You automatically succeed your saving throw when you roll a natural 20. However, rolling a natural 20 on a saving throw does not allow you to draw any critical hit cards; there is nothing to critically hit with your success!
Weapon Focus and Critical Hits: If you possess the Weapon Focus feat with the weapon that you confirm a critical hit with, you can draw 1 additional card and choose which card to apply against the critically hit creature. The card not chosen is not applied and is discarded. If your weapon’s critical multiplier allows you to draw multiple cards, you can substitute any card drawn for the Weapon Focus card.