The Critical Hit Deck is when you confirm a crit, you roll a d% (or 2 d% if its a x3 weapon, 3 d% if its x4, etc) and pick one or more cards according to that. I'm using the d% instead of picking a random card, because I do not have them as a physical object. Depending on what card you get, and what weapon, much insanity could happen. You could rupture their intestines, causing them to bleed Con until healed or they succeed at a fort save, you could smash their teeth in and make it so they can't cast spells easily, etc. All you'll have to do as a player is roll the d% and if you have a high multiplier, you can pick which effect you want.
The critical fumble deck is similar, but has things such as you damage yourself, you throw your weapon, you hit your armor, etc.
If the group doesn't want to use that, I'm fine with that. It just adds flavor to combat other than "I roll a natural 20, confirm, and deal twice as much damage to him." or "I roll a natural 1 and miss."
