#daisy chain of thanergetic link from her corpse to the sword and from the sword to Harrow

[mayasaura]

The how Alecto got into Harrow to be Nona question is pretty easy to explain using the information Augustine gives us about revenants! Ghosts can follow thanergetic links that are created by contact with the deceased's thanergy. In the case of Harrow and Alecto, the link was created when Harrow touched Alecto's body in the Tomb. Alecto follows the link, finds Harrow's body without Harrow in it, takes the opportunity to hop inside, and bingo! You get a Nona.

And ghosts very much do just jump on bodies, especially in the River. Mercy explictly warns Harrow about the possibility of exactly that happening.

A Lyctor’s body, empty, with its battery intact but nobody in the driver’s seat? Do you know what could take up residence? Anything could get inside you—any horrible or evil or lonely thing, any miserable revenant, or worse—and you, you Ninth House child, are not remotely qualified to fight an outside predator. You are like a little baby. Listen to this: if we get to the other side and find you’ve gone and left your soul behind—I will separate your brain from your skull without waiting for you to catch up.

Anything could get inside her. Possession is a risk from any ghost, ghoulie, or devil that happens to find her.

Let's use Wake as an example. She definitely does not have any soul-sharing bond with Harrow, and has never become a lyctor. Abigail explains to Harrow that the Sleeper is laying seige to Harrow's subconscious with the intent to oust her, and concludes her explanation with:

Right now, in this moment, you are alive��let us ensure that if your body survives, you will remain at the helm.

The meaning is not ambiguous. If they fail, and Harrow's soul is killed here by the Sleeper, the Sleeper will possess Harrow's living body in the waking world. Abigail, the preeminent expert on ghosts and revenants, takes this as self-evident.

Possession is a risk when dealing with any revenant. No one needs to have consumed a part of another person's soul.

Once again I find myself agreeing with your conclusion that Gideon and Harrow's souls are acclimated to one another's bodies while disagreeing with your proofs.

Even if you're entirely right that Harrow planned for Gideon to surface, we have no idea if Harrow would know her body rejecting the possession was even a risk. We get that information from Pyrrha, who is in a unique position to know more about soul transfers and body sharing than just about anyone. I would hesitate to assume that Harrow, who describes her own knowledge of spirit magic as "execrable," has all the same knowledge as Pyrrha.

If I were to point to evidence of how becoming a lyctor effects ghostly possession, I'd look at Ianthe's steps five through seven.

Step five, incorporate it: find a way to make the soul part of yourself without being overwhelmed. Step six: consume the flesh. Not the whole thing, a drop of blood will do to ground you. Step seven is reconstruction—making spirit and flesh work together the way they used to, in the new body.

Step six especially. If the cavalier's flesh needs to be involved for grounding, it follows that step seven—making spirit and flesh work together the way they used to—anchors the soul of the cavalier to the lyctor's body as if to its own, and prevents the lyctor's body from rejecting it.

Harrow never completed step five, but she did perform the ritual completely enough that she was able to wield Gideon's sword against Cytherea. So odds are very good that her body wouldn't reject Gideon's soul.

Yeah, we are waaaay far away from the original point of Pyrrha being doomed by the narrative 😂 But I fucking love talking about necromantic theory, too. There are so many little details tossed out to us as they become relevant, and so far, they've all linked up to create an increasingly coherent picture.

Pyrrha feels so doomed by the narrative, I thought for a long time she was probably secretly dying according to Anastasia's tripod principal, the body only being able to go on for so long without G1deon's soul. But taking a second look .... nope.

The tripod principal says body plus thalergy plus soul equals life. The body in equilibrium produces thalergy, so it shouldn't matter that the soul, Pyrrha, is technically dead. It wouldn't work for most ghosts—a body will usually reject a transplanted soul and start shutting itself down, like Nona—but after ten thousand years a lyctor, the body has adjusted. Pyrrha's got squatter's rights on life.

She still feels pretty doomed to me. She's so fucking old and knows too much and has too many regrets. But if she is, she's gonna have to die of being killed.