Recs.
Updated
You are a breach mage, a guardian of Gravehold in a post-apocalyptic setting. Team up with 1-3 of your friends (or even try solo) against a reality-destroying horror besieging your city.
Mechanically, this is a deck-builder (with all the expansions that entails) with (almost) no shuffling -- instead, when you would draw from an empty deck, you simply flip your discard over. This twist on the genre gives veterans an extra puzzle to think about.
Specs
Pros
Pro Challenging for the right reasons
Many cooperative games suffer from a certain degree of "solvability". This doesn't necessarily mean you can win every time, but once your play is optimized or close to it the challenge is very apparently "are the card(s) shuffled in an order than allows us to win?" (e.g. Pandemic). Losing in Aeon's End -- and you will lose with some regularity -- feels like a lesson in efficiency.
Cons
Con Minimal randomness
Sometimes the fun of a deck-builder is throwing things together and getting a good shuffle out of your engine every once in a while. Aeon's End is minimal-randomness, so you'll never luck into a synergy you didn't plan, and it's possible to wedge yourself into a bad card order at a time when you really can't afford to spend a turn to deal with it.