Fortunately for Alana there is an answer to that question. It's a strange one, to Fingon's mind (perhaps for anyone who is not the Null, really,) but it does exist.

"Apparently the gods' race and the Null lived together, once. But the powers of the gods' race induced emotion in the Null, perhaps for the first time ever. They decided to slaughter their former allies, rather than continue existing as beings that could feel."