When it comes to Orsa, essence is key. To imitate an essence, namely Harken's its extending and reconfirming yourself inside of Orsa. Harken, when tied to Seven has a flux and counter flux of the very same essence. The essence doesn't change, granted the immitation you used could only duplicate it, there is no specification of it being the same essence. If you say its the same, then I can destroy it namely because its the same 'or similar' as which has been stated in my post.
Its either we lock each other fighting for control over the ecto-essence (seven's conduit) or the non-living/similar if not the same (raziian's outlet). Initially, as I said, if its of a similar essence, Seven can manipulate it because he is of the alignment. Which would serverly limit Raziian to the living aspect.
If your imitation is up, its fighting Harken. Since it would've emulated the same thing I was already doing to you, it'd make sense to push my armament to negate and loop the impostor tying up all of it's attachments and detaching of the ecto-essence thats spanned about Red City.
As far as Nightmare-mode. Its when Seven disbands his current individuality and develops a sentience to Naught. Namely the source within Orsa, or the one that dominates this Affinity. Garforge Temblin (the seventh son's father), now unlike the Omniverse, the Devoid/Naught within Orsa doesn't disrupt the boundaries or threaten it. Namely because it is refined and defined as an entity, Garforge. When Seven becomes 'Dark Cry' he becomes a force, of the divine and effectively tied to his original outlet of birth. "Fear". He pushes it so far that 'Fear' becomes 'Insanity' or the coined term, 'Madness'. The move is of the psyche, and can overpower the senses, of a linear notion.