Numenera: Ghosts of the Past
All PCs are sufficiently strong, smart, and agile, but your stat pool is the extent to which you can do these things and not overly exert yourself. That is why it is designed as a pool that diminishes. It also acts as your HP to a certain extent. You use your pool to do actions, cast spells, and absorb damage from enemies.
If your pool is the basic measurement of your stat, your edge reduces the cost of doing those abilities. If you have an ability that uses 3 Intellect and you have an Int edge of 2, then the ability only costs 1. If you get the ability down to 0 through edges, then you do that ability for free. It’s better to have 10 might and 3 edge then it is to have 20 might and 0 edge.
Applying effort reduces the fail chance of an ability. It requires spending points from your pool. To apply 1 “step” of effort (reduce the difficulty by 1) you must spend 3 points from the appropriate pool. Only the first step costs 3 points. Subsequent steps cost 2 points. Your effort score is the maximum amount of steps you can lower a difficulty through effort. When you apply effort, you subtract your edge first. Therefore, if you have 3 edge, you can always apply 1 effort for free. And if you have 5 edge, you could apply 2 steps of effort free (3 for the first, 2 for the second).
Effort and Damage
Instead of reducing the difficulty of an attack, you can apply effort to do more damage. For each level of effort you apply, add 3 points of damage to your attack.
For AOE attacks, using steps of effort does 2 damage, instead of 3. It does it to all targets in range, furthermore, if the enemy resists, applying effort guarantees 1 point of damage.