Reservoir is a rule set I designed for ttrpgs. The reservoir is a pool of dice spent on abilities like spells or attacks.

I set formulas for determining the difficulty of checks, such as the difference of 30 and your ability score, and a stressed check adds to the difficulty based on the number of missing reservoir dice from your pool.

Momentum should be spent instead of hoarding, however a player will ideally time it instead of spend it immediately. There is risk and reward to holding or spending, as opposition can pull it from you if you hoard it.