Lunatic (Feat)

Individuals taking the lunactic feat are tied to the lunar cycle. They are at their best during the full moon and at their worst during new moon. During the gibbous moon they enjoy bonuses to attack rolls, Fortitude and Reflex saves, and Charisma-based skills. The reverse is true during the crescent moon. The sway of the moon on the judgement of individuals with the lunatic feat is such, however, that Will saves suffer a penalty during the gibbous moon, peaking with the full moon, and enjoying a bonus during the crescent moon, peaking with the new moon.

References

Ravenloft Campaign Setting, p. 48