Harry certainly learned how to operate Demonreach, but he has not applied anything he learned from Demonreach to his own personal magical or personal development.
I don't think the runes on the new staff he made from a branch on the island glow green instead of the previous red/orange as a mere coincidence.
What is the odds that Harry picks up a ghost companion, if only for a single book. I think Ghost Story established that ghosts are not the normal. Most people "move on" when they die. So I am not expecting a ghost of Susan or MacFin to be following Harry. But occasionally ghosts do form. I am expecting Harry to be "hired" by a ghost at some point :)Might be interesting if the reaper we saw pays him a visit.
Might be interesting if the reaper we saw pays him a visit.
Can gods have ghosts?Of course. Think that's a bit of the problem. Undead 'spirits' trying to enforce their will on reality, trying to come back through/drop the veil.