Balance? If that's so, it'd explain why only those of us who have spiritual or magical powers seem to have been sacrificed. [The Bridge was probably there to make sure the energy was properly spread then, seeing that she doesn't appear to be linked to any element.]

Something bothers me, though...the spirits haven't said before that they need us. What would happen if the sacrifices stop? [Whether it's stopped since the altar was destroyed remains to be seen, and if this DC had anything to do with the matter it would complicate things.]