Can Demonreach do this?

[Lord Kinbote]

Release Thomas but keep imprisoned his demon, the one that makes him a White Court vampire?  That would effectively make Thomas human again.  I believe there's a hint somewhere in canon that separation is possible.  Why not DR as the instrument?

That would make for a nifty but conflict-laden solution to Thomas' status/prognosis.  At the end of Battleground, it's stated that Thomas is on the verge of death and wouldn't survive being released from DR unless he can immediately feed on a human to the death.  But I can't see Harry letting that happen even if Harry hated the human in question, but such a release and feeding undoubtedly will be what his 'intended'/'wife' will demand. 

But if DR can separate Thomas from his demon, Thomas isn't available to make that call (basically because he's unconscious unlike other DR inmates).  Would Harry take on responsibility for making that call on his own?  Lara would be vehemently opposed.  More conflict.

Also, can DR separate the One Who Walks Besides/Nemesis/Nemesis infection from its host like Justine?  And DR keep OWWB/N/N infection as a prisoner?

BTW, not clear to me at all how the OWWB/N/N infection works.  I can't believe the OWWB is wholly encompassed within Justine (and  was once wholly encompassed within Harry's godmother), and that others can't be simultaneously infected. 

[Conspiracy Theorist]

It would kill Thomas, his Demon is the only thing keeping him alive.

Demonreach can parole a prisoner, Harry could release Ethnui but bound to his orders, so he actually has an island full of superweapons not just an armoury. He can probably separate a Mantle from the holder, and release the holder without the Mantle, but this would result in someone like Molly being left incapable of functioning as a human being. Same dilemma as Susan, same solution. An unravelling of the Mantle.

Thomas needs to be released and fed immediately with the richest most inexhaustible life force available, a normal human would not be enough, it would kill them and would be a deal breaker. The Winter Lady, an immortal might do it, and would probably survive the ordeal. Mab would be even better and would definitely survive. As Mab one said about Thomas becoming the Winter Knight “Human enough” so I suspect it goes both ways, Mab and Molly both originally human are probably “Human enough” for Thomas to feed on them. Mab would probably approve of having the human sucked out of Molly.

Harry has The Shroud, so he could use that to sustain Thomas during the feeding.

[EBRIEN]

Just need a Bigfoot.

[Ed0517]

I tend to think Demonreach is a blunt force object, and removing the demon is a delicate operation. It needs a scalpel, not an ax.

[vincentric]

I tend to think Demonreach is a blunt force object, and removing the demon is a delicate operation. It needs a scalpel, not an ax.

I think Demonreach has the power, but it must be linked to a Warden with the skill to perform the spell. Currently that is beyond Harry's level.

[Conspiracy Theorist]

Just need a Bigfoot.

We haven’t seen a female Bigfoot.

[Regenbogen]

We haven’t seen a female Bigfoot.

Who says it has to be female?

[g33k]

To answer the OP -- I don't think we know if Demonreach can/cannot do this.

Offhand, I suspect "cannot," but AFAIK we have no hints about Demonreach's abilities in the text.

[Ed0517]

I think Demonreach has the power, but it must be linked to a Warden with the skill to perform the spell. Currently that is beyond Harry's level.

We don't know if it even can be done. Do we have any record of any wizard cleaving off the demon? Maggie was a wizard of skill, and had plenty of opportunity. Did she ever split one off?

[Regenbogen]

I was thinking: maybe it would be possible to make the demon sleep, instead of separating it. Like Lea did with Susan and Martin. So technically Thomas would be awake and possibly alive after intense feeding WITH his demon still there but inactive.
I can imagine, that Demonreach could do that.

[g33k]

We don't know if it even can be done. Do we have any record of any wizard cleaving off the demon? Maggie was a wizard of skill, and had plenty of opportunity. Did she ever split one off?

I was thinking: maybe it would be possible to make the demon sleep, instead of separating it. Like Lea did with Susan and Martin. So technically Thomas would be awake and possibly alive after intense feeding WITH his demon still there but inactive.
I can imagine, that Demonreach could do that.

We don't know that it can be done, no.  I suspect the same method Lea used on Rampires won't work on Whampires, but I guess it depends on whether Jim has addressed this in his own internal metaphysical headcanon... and if not, how Jim wants it to work (but I note than Jim "seldom" wants Harry to have a ready solution in-hand!).  I still like the idea (don't recall who proposed it, sorry) that the Swords each have a Whampire destiny:
Raith/Lust/Love/Amoracchius (and Thomas Raith as the KotC to wield Amoracchius against the Outsiders)
Skavis/Despair/Hope/Esperacchius
Malvora/Fear/Faith/Fidelacchius

I suspect Margaret LaFay couldn't really experiment, tho:  Papa Raith would likely frown on any wizard working out a method to un-Whamp someone, it would be too huge a vulnerability once the method (inevitably) got loose.  So no, she didn't have an opportunity (IMHO).

[Regenbogen]

We don't know that it can be done, no.  I suspect the same method Lea used on Rampires won't work on Whampires, but I guess it depends on whether Jim has addressed this in his own internal metaphysical headcanon... and if not, how Jim wants it to work (but I note than Jim "seldom" wants Harry to have a ready solution in-hand!).  I still like the idea (don't recall who proposed it, sorry) that the Swords each have a Whampire destiny:
Raith/Lust/Love/Amoracchius (and Thomas Raith as the KotC to wield Amoracchius against the Outsiders)
Skavis/Despair/Hope/Esperacchius
Malvora/Fear/Faith/Fidelacchius

This is one of the possibilities I like too.
Or it will be a combination of sword and Demonreach.

I suspect Margaret LaFay couldn't really experiment, tho:  Papa Raith would likely frown on any wizard working out a method to un-Whamp someone, it would be too huge a vulnerability once the method (inevitably) got loose.  So no, she didn't have an opportunity (IMHO).

I am starting to suspect that this kind of knowledge could have been why he hunted her down. She found something out he didn't want her to pass on. Probably the knowledge is there somehow. Could be with Lea and Harry just has to ask the right question. And first he has to know that there is a question to be asked. So not exactly an easy way.

[seanham]

Could Fidelacchius kill the demon side but save the human side?

But to take this a step further, how would Thomas react if this was possible? For years now, he has been tormented by his demon, but it allows him to be an ally to Harry, do good for other people, serve in the Oblivian war, and protect his girlfriend. Yes, he probably hates his demon and the need to feed on people, but he very well could feel useless for being a vanilla mortal and need to relearn how to live.

[Ed0517]

I was thinking: maybe it would be possible to make the demon sleep, instead of separating it. Like Lea did with Susan and Martin. So technically Thomas would be awake and possibly alive after intense feeding WITH his demon still there but inactive.
I can imagine, that Demonreach could do that.

I expect it is the demon that actually feeds, not the "human" side. So the demon has to be active

Also, Martin and Susan were born human. Whamps are born Whamps.  Nothing to go back to. 

[Ed0517]

I suspect Margaret LaFay couldn't really experiment, tho:  Papa Raith would likely frown on any wizard working out a method to un-Whamp someone, it would be too huge a vulnerability once the method (inevitably) got loose.  So no, she didn't have an opportunity (IMHO).

Margaret looks like she could have taught sneaky to Harry. She was evading the Wardens for years.  I think the question is more would she have had a reason to try