The Critical Hits deck contains 52 cards, and each one has four different effects based on four different types of attacks - bludgeoning, piercing, slashing and magic. Magic only comes into play when there is an attack roll involved. When a player scores a critical hit, they draw a number of cards based on the critical multiplier for their attack - one for x2, two for x3 or three for x4. The player then chooses one of the cards they drew to take effect for the type of attack they are using. The rules insert suggest that GMs only use the deck for special NPCs as the effects can be pretty dramatic.

Some of the cards only have a special effect, but most of them do double damage plus an additional effect that may involve a chance to save to resist. One time, a boriwog barbarian scored a critical with his battle axe. The player chose a knockback from the cards he drew that pushed the hydra fighting the party back 1d6 squares. Another time, the houndling ranger hit a critical artery with a critical hit card in which the enemy had to make a Fortitude save or die. The other memorable moment was when the human sorcerer hit a guard with a scorching ray that didn't quite kill him but caused flashing sparkles to stun him for a few rounds. The party was able to get in the gate without him sounding the alarm because of it after their initial plan had already failed.

Overall, the deck added more drama to the combat any time a PC struck a critical hit. Doing more damage is fun to do, but it's even more fun when there is something descriptive that has an additional mechanical benefit to go with it. I'll definitely be using the critical hits deck in all my games now, and I highly recommend purchasing it for your Pathfinder of D&D 3.x game.