Gibbous Blade

Weapon (longsword), rare (requires attunement)

Absorbing the mysteries of ten thousand lunar cycles, this longsword has come to reflect the moon’s wax and wane. + Before you make your first attack of a combat encounter with this sword, you declare whether the sword is in its waxing or waning phase. At the start of your next turn, the sword enters its opposite phase and continues to alternate in this manner until the end of combat. + While the sword is waxing, you have advantage on attack rolls with the sword until the start of your next turn.

While the sword is waning, you have disadvantage on attack rolls made with the sword until the start of your next turn, or until you miss with an attack, and attacks with the sword deal an additional 1d6 radiant damage.