As far as she knew, they were antisocial and asexual, and there were fewer of them than other types of Crescents, probably because males outnumbered females by a large margin.
Well, actually, if they're asexual that's probably a good reason that there's fewer of them. Sexual desire and attraction is usually helpful to procreation.
And now Caidos are also Crescents?? WTF? I thought I had it all straight, and now I'm confused again.