sometimes I see people being confused where alectostasia ship came from so here’s a little bit of run down

I’m not really good with words so it might be clunky

what we know from the text

• Anastasia tries to achieve ‘perfect lyctorhood’, something goes wrong during her ascension, John kills Samael, Anastasia fails her attempt
• Anastasia moves to the ninth, continues working on the house or only founding it at that time
• John asks Anastasia to help build the tomb ’I built that tomb with Anastasia, designed every inch of it.’
• somewhere between working on it and Alecto’s entombment, Alecto and Anastasia make a vow where Alecto basically swears as a cavalier to her ’Alecto said, I remember my vows. As I swore to Anastasia I swear to you. I am in your service until you bid me the favour, and whatsoever you appoint I shall perform, and consider the vow rendered. This is what I promised, until such a time as you deal with me as you see fit.’
• as John leading Alecto to the tomb, she asks to see Anastasia ’She had said, There are almost no beautiful things left. Where is Anastasia? Let me talk to Anastasia.’
• presumable Anastasia is the one to inflict to the ninth house importance of keeping her bloodline and worshiping of the tomb through all of those years
• Anastasia’s bones are in the tomb ’She looked back beyond, and she saw Anastasia, tucked where nobody would find her: Anastasia, all bones. Not really Anastasia. But Anastasia’s body without the meat on it, snuggled right into the curve of the rock, ready to close the door whenever it was opened. She remembered Anastasia.’
• Alecto immediately getting chill after tasting Harrow’s blood ’The child was silent; but her blood was on Alecto’s lips, and through that blood Alecto was made to understand what it was, and was astonished exceedingly. Alecto put away wrath and said: Thou art the blood of the tomb-keeper.’
• Alecto saying sorry for Samael

the implications

the vow on itself is very interesting, at first we all know how usually normal cavalier and necromancer relationships are. then for Alecto to comply to that, indicates she should be pretty trusting of Anastasia, and their relationships at least somehow better than with other lyctors who were terrified of her

then there’s also the tombkeeper blood thing, what serves as a check note for Alecto after waking up, and means the initial purpose of the ninth house was actually waiting for rock to roll away

and one part of the vow seems to imply 'if anyone beside a tombkeeper wake you, slay them as they came to hurt you’, as could hinted on a protection from other lyctors who wanted to kill Alecto? (Then Alecto remembered the vow, and turned back upon the altar to face the second child and raised the sword with wrath in her heart, for they meant to bring destruction upon her.)

then the matter of Anastasia’s bones laying in the tomb next to the rock. not sure if it’s just her skeleton or she made herself a some construct mechanism from her bones. and not clear if she got entombed on her own volition or John closed them both there, but being entombed together five feet apart cause we are not gay

there’s also some oddness in Alecto immediately after waking saying she’s sorry for Samael, but I won’t go into that here, anyway Anastasia was trying to find a better way to lyctorhood and I think in her more close relationships with Alecto she figured out something that John wasn’t telling them, before or after her ascension

and some theories

I think I first heard this theory from @/mayasaura, that ninth house tradition of telling secrets while submerged in the salt water could’ve corelate with Anastasia trying to have a talk like that with Alecto since she feels the most at ease in the salt water, so means pool time for alectostasia too

another one that I really like but not sure how much legs it actually would have in canon, one of the reasons Nona was so enamored with her body cause Harrow is a spitting image of Anastasia, first saw @/corvophobia talking about it

coming back to Harrow, could there be anything more to her taking immediate affection to the Body a la some fuckery with Anastasia’s spirt/tombkeeper’s blood

more people explained it better, I try to reblog most of the theories in my side blog, you can check it out there but some of it explicit just in case

anyway in conclusion, as I keep procrastinating with my work, I don’t think they were making out 24/7 in Canaan house in canon but something for sure happened there between them