Lena's family sure likes the moon. It's kind of like when you tell some obscure relative that you like butterflies, and for every birthday and holiday until the end of time, they get you something with butterflies on it. Someone in Lena's family must have done that back around the time of the American Revolution, because, man, those Duchannes and Ravenwoods have moons everywhere. They're over doors, in crypts, on boxes, and even hanging around their necks.
(To shake things up a bit, we suggest throwing some waxing gibbous moons into the mix. They really open up a room.)
Besides being a nightmare for Nate Berkus (he really should branch out into crypt redecorating—there's money there), what do all the moons mean? Well, it's simple, really. We'll let Amma explain: "Half-moon's for workin' White magic and full moon's for workin' Black" (10.9.61).
Simple, right? Well, what about all the crescent moons in the book? Lena has a crescent moon birthmark on her cheek and another on the chain around her neck; Ravenwood has a crescent moon carved over the front door; The Book of Moons is adorned with a great big honkin' crescent moon. We're not sure if these crescents are waxing or waning, but it hardly matters. What does matter is that the crescent moon is halfway between half-moon and new moon or, as you might call it, no moon.
So let's recap: half-moon represents Light; full moon represents Dark; and according to Ivy, "no moon is somethin' else altogether" (10.13.187). That means the crescent moon is somewhere between Light and the unknown. That's a good way of describing Lena, don't you think?