We know that the traveler and the light likes to reveal itself to us in the form of a hawk or falcon, and in the past, I've speculated that the star horse seen hanging around the 9 could be the representation of the darkness. However, I feel in makes sense that the star cat could actually be the darkness (or its representation) For starters, cats and birds are natural enemies just like the light and dark. Next, nearly every time we've encountered the star cat, it was in the dreaming city, which was created by the clash of light and dark. Finally, the awoken seem to worship these cats as we find statues of them all around the dreaming city and in Y2 we even made offerings to them. This could also explain why Mara Sov keeps the star cat at her side in the helm, since the awoken use both light and dark powers. And while it could be a stretch, this might explain the cat on Neomuna, which has the veil and is strong in the darkness. On a side note, there could be a real world connection as well since the Egyptians build the pyramids and worshiped cats. So this could be where bungie drew some inspiration.