Edit 2: Spellcheck. Whoops, didn't realize my spellcheck wasn't working on this text field!
Buffer Overflow should not be to impact the Scion Reserve pile just like Buffer Overflow can’t prevent another member of the Ennead from entering play.
Technically, neither Ennead members nor scions “enter play.” They are simply moved from their reserve areas into a play area. The phrasing is a little different, but neither goes from out of play to in play. Exploit Vulnerability shouldn’t work on either of them, either, for example.
However, if Phrase overflowed an Aeon Man, what card would be played? I’d say the heroes could choose between the OblivAeon or Scion deck (assuming both OblivAeon and a scion were present in the zone).
If Parse stopped an Aeon Men deck card play then it should work like Team Villain games and you’d play the next card of the Aeon Men deck.
I think what stops the Ennead from being affected by Buffer Overflow is text from The Shrine of the Ennead and I can't find any similar text for the Scion Reserve.
The Shrine of the Ennead text: Whenever a Villain Target would be destroyed, flip it over instead. This card and all cards beneath this card are indestructible and cannot be removed from the play area by any means.
Edit: Whoops, didn't see past the first response.
So are all of the Ennead and the Scion Reserve considered in play from the start of the game? In that case, it makes sense to me that Buffer Overflow couldn't target a scion being moved out of one... area? of play to another. But it doesn't make sense to me that they would never enter play and still be part of play.
I completely forgot about the team villain rule clarification. That's good precident and a rule I'll try to remeber to follow, but I still wish the clarification was in the book. xD
If they had all of these clarifications in the rulebook it would be heavier than the filled Collector’s box 
Is the oversize Scion Reserve card considered not-a-card, a character card, or indestructable? Because otherwise I don't see anything protecting it from being destroyed by Argent Adept's Cedistic Disonant now that I'm taking a closer look at it.
It’s not a card in play it’s a rules card like the colosseum for Kaargra
I just want to correct this. Exploit Vulnerabilty would totally still work. As it is a "target entering play". While frequently a target entering playing happens at the same time as a card entering play, there are a few instances where it can occur even when a card has not entered play. Imbued Vilitality and Miss Information flipping are another two examples.
Ah, I forgot that “gains/loses [keyword]” triggers “[keyword] enters/leaves play.” It’s consistent with Faultless, at least.
Okay, so to make sure I've got all this right:
1. Parse's Buffer Overflow doesn't work on Scions, because the Scions aren't villain cards. Villain cards come from villain decks. So Buffer Overflow can work on the Oblivaeon, Scion, or Aeon Men decks, but not the Scions or the Ennead.
2. A Scion entering play will trigger Parse's Updated Intel card, but she can't look at the bottom of the Scion pile, because it's not a deck.
For point two a Scion entering play in the same Battle Zone as Parse would trigger Exploit Vulnerabiltiy not Updated Intel
Incorrect. Lead From the Front only works on damage from villain cards, for instance, and of course it works on damage from any villain character card. It doesn’t work because they aren’t entering play, they’re already in play. So Updated Intel would also not work.