The moon nymph's connection to the moon affects its power as the cycles of the moon progress. The statistics given represent a moon nymph during a crescent or gibbous moon.&nbsp;During full moons, the challenge rating increases by 1, the creature's hp maximum increases by 30, it has advantage on attack rolls, and all saving throw DCs increase by 1. Inversely, during new moons, the challenge rating decreases by 1 as the numbers move in the opposite direction.