The basic mechanic

The basic mechanic for Chains of Aether is pretty simple. Basically you just add your attribute plus skill (lower is better) together. This gives you the target number for a task of average difficulty. You then play a card. If the card's value if above the target number, the task is a success. The higher it is above the target number gives you the degree of success.

For tasks that are more difficult than usual you would increase the target number. For easier tasks just increase the value of the card.

So, why the cards and card pools are important:

The basic idea of card pools is to allow the player to think tactically a bit and hopefully to encourage him to describe his actions with little fear of them failing. Under most circumstances you will know whether or not you action is successful ahead of time because you get to decide which cards you are playing.

The other reason card pools are nice is because they allow for Chaining. I'll go into that in a bit more depth some other time, but the basic idea is that the number of actions you are capable of in a round is only limited by the size of your card pool (though you can spend to add items to a chain). As you describe your actions, you play a card.

I leap up on the table [play a card], kick the guy's shield out of the way [play a card], punch him in the face [play a card], and stab him with my sword [play a card].

This gives two benefits. First, the only action that really matters is the last one, but you increase the degree of success by the amount that each action beat its target number (target numbers are set by your lowest skill used), less one for each action attempted (this number needs to be playtested, but it feels right for now).

Second, each chain has a pay-off. The strength of the pay-off is determined by the number of actions successfully chained.

Like I said, I'll go into this in more depth later, especially its non-combat applications and how it works with allies, but hopefully this is enough to give you the basic idea.