So that magical Azeroth globe in Ulduar had me wondering:
Why depict one of Azeroth's moons as a crescent? What would be the purpose of that? Its a crescent from every angle, and Azeroth and the second moon aren't shown as crescents either. I think that the moon actually IS a crescent. At first I thought we would get a cool story about how part of the moon got obliterated Sonic Adventure 2 style, but then it hit me. Elune, should she actually live on the moon, wouldn't let that happen. But then what if she didn't live on the moon? What if she WAS the moon?
An inorganic crystal-like being that radiates Light, a naaru. Velen had suspected that Elune was a naaru, and Velen knows what he is talking about. I don't think there would be a being so powerful and so similar that he would not know about it. It has to be. But then we learn in Legion that Elune created an Elder naaru near the beginning of the universe. That would make her far more powerful and far older than the naaru, right? Well, not necessarily. Naaru are geometric beings that consist of a single core radiated by smaller crystals. A core with an orbit...much like everything else from atoms to galaxies, everything follows a pattern.
That is what Elune was, an enormous naaru with the core the size and shape of a crescent moon, whose smaller orbiting crystals would one day become prime naaru like Xe'ra. Why do I think this? Well, we learn that naaru somehow reproduce. O'ros is called the last of Xe'ra's line. How would an inorganic being reproduce? By creating a new being from its own self, asexually. In other words, creating life from itself. That would later grow more and more, until the offspring itself was able to reproduce.
Take in infant Naaru like K'ute. Likely born from M'uru as the achievement that rewards him suggests (drinkin from the Sunwell). Born from M'uru who was born from an older naaru, Likely A'dal considering his presence in the Tempest Keep, who was in turn born from naaru tracing all the way back to a prime naaru, siblings of Xe'ra, born directly from the physical incarnation of Light itself, Elune, a naaru nearly the size of a planet. Just like an electron orbiting a nucleus which makes the atoms that form a moon which orbits a planet which orbits a star which orbits a galactic core, everything has a pattern.