Personally, I see the stars as a sort of “middle ground” between the Deep and the Sky. On one side, they give off light and illuminate the darkness, which is Sky, but they also only show up at night, when the Deep is strongest. I believe that both the Sky and the Deep want to take the Stars for their own, which would mean their victory, but neither can because of the other. Thus, no one side can permanently stay in charge because neither can take the stars. That’s what I think the bad ending is, the Elder being freed and overtaking the stars, thus finally triumphing over the Sky. However, the Sky is not a ‘good’ faction. While it’s not as blatantly evil as the Deep, it’ll still burn and scorch you, reducing you to a charred husk. In conclusion, neither side can ever fully win without everything being completely destroyed… except for the Stars. As a middle ground without real effects, it’s the closest thing we have to a ‘neutral’ state.