Coop is pretty fun. From what I remember, every character has innate skills and a unique deck of cards. The card played will determine things such as movement, attack area, damage, etc. as well as play order as cards had 5 (i think) levels of speed that would determine the order players take their turn (reminds me a little bit of Gloomhaven). After a card is played, it has a value associated with it (1-3) depending how powerful it is. This number determines where it is placed on a refresh track. Each turn it advances on the track before returning to your hand. More powerful cards can thus be used less frequently.
An AI villain deck determines villain and mob movement (I think there may also have been a dice involved). Those cards are each drawn on your turn to determine enemy movement and attacks.
Overall, the game is fun. I was able to play some Apostate during a prison riot with guards and prisoners swarming the area and us trying to find an artifact and escape. It was fun and strategic as we really needed to conserve cards and play carefully to ensure we were able to hit hard when we needed to and run fast when needed. Also had to work as a team to avoid splash damage from attacks as many hit a zone indiscriminately.