Since we're talking about Demonreach, have you considered as long as the prison exists and needs a human Warden, that Ivy can't win the Oblivion War?
Why yes I had. I made that point a week or so ago. Harry is of course oblivious to that particular conflict. This may explain why she snubbed Harry, someone (probably Thomas or Lara, her agents) told her or recorded the fact that Harry was the Warden.
To be correct she needs to wipe the knowledge of those beings from mortal minds, not of Demonreach or the Outer Gates themselves. Harry has of course been going through the roster of prisoners, making that much more difficult, oblivious as always, but HP Lovecraft and Frank Belknap long have a lot to answer for even vanilla mortals know about the Hound of Tindalos. Ivy is losing. Look at the impact of Cthulhu in popular culture. She having as much success as Mab had against Disney. Frozen anyone?
It’s bad enough Harry got between her and her surrogate father, but to find Harry has also got involved in an existential crisis undermining her whole existence and purpose is the cherry on the cake. No wonder she cut him dead. And he clearly has no knowledge why.
