Card sets, and the one card you cannot get

Cards drop from the pusher and from the slots. Collect them into sets, and a completed set pays out a reward worth chasing.

A new set releases every two weeks. The catch is that not every card is awarded to every player, so there is almost always one gap you cannot fill on your own. That is what trading is for.

We have watched this pattern work in other games for years. It only works if the trade feels like a favour rather than a transaction, which is the part we are spending time on.