About the Shadow (spoilers)

[Apjjm]

I always thought of the sequence of events played out in such a way that the shadow was no longer after you (until you got captured).
Alexander took your orb, so the shadow was not interested in going after you. The guardian was after Alexander to reclaim the orb and you just happened to be in the way. It never explicitly chases you until you collect 6 pieces of an orb. Only then do you draw the shadow's attention as you have an orb (I'm guessing it isn't particularly fussy which orb it posses). When you use the orb to destroy the barrier, the shadow goes after Alexander again to collect the remaining orb.
Each ending then fits, if you let Alexander get away, he leaves the orb behind and you get killed. If you keep Alexander there, the shadow kills him, as he is now the owner of the orb.

Not really answering the question there, but it's how I always saw it. I like it when things are left open to interpretation.