User blog comment:Blaziken rjcf/My prediction for Alpha and Omega/@comment-87.116.253.143-20160527163737/@comment-26271908-20160529055820

I agree with Blaziken. Death is just the embodiment of the concept of death, not the concept itself, just like the Endless are just perspectives of that said concept and, if they are killed, another person will simply start to personify that concept (It's easily explained by that comment in Sandman's The Wake where someone comments that, in Dream's funeral, they are actually grieving for a point-of-view)

Death was the original and first embodiment of death, hence why himself is called Death. Now that he is gone, Billie is the new personification of the concept. It would explain why the Natural Order is still intact