Speaking of Iosefka, I want to use her to launch off another fairly important question that isn't getting much discussion. Iosefka's relevant to this conversation, so bear with me.
We know she wears Choir clothes, she's one of the few people in the game happy about being Great One pregnant, she's turning people into Celestial beings (notice that the beings you kill in her lab don't disappear, indicating they were NPCs), and there's strong evidence she's not the real Iosefka. She also uses the Augur of Ebrietas in battle, which indicates she must be in the Choir because the description of that item straight up says "Hey, people in the Choir use this since they got close to Ebrietas."
When you actually explore her lab from the back, you discover a number of important items, but the one I want to hone in on this time is the Cainhurst Summons. The item description (bolding mine):
"An old blood-stained summons, inviting an honored guest to the forsaken Castle Cainhurst.
Rather bafflingly, it is addressed to you.
Do not hesitate; the stagecoach leaves from Hemwick crossing."
The one place in the game that you are guaranteed to be without any memory of how you got there is Iosefka's clinic, which is where you find the summons. It is not on your person when you wake up, but rather, hidden in the back where Iosefka clearly doesn't want you going, to the point where she'll turn hostile if you approach her prior to Rom. We can assume, as a matter of course, that the item description is being truthful if not vague. There's no reason to think the summons is not meant for you.
So an assumed series of events can be:
> Get summoned to Cainhurst Castle
> On your way to Hemwick Crossing, you end up in Iosefka's Clinic in Central Yarnham
> Either the unidentified man from the beginning or Fake Iosefka takes the letter off your person and hides it away
> You wake up with no memory of why you're going to Cainhurst
Cainhurst is, at the time of the game, abandoned.
No one should have been able to summon you there. The only things that remain there are seemingly undead servants, ghosts, Logarius, and the Queen of the Vilebloods. Let's go ahead and throw out the servants and ghosts as reasonable guesses for who summoned you, which leaves Logarius and the Queen. Of the two, Logarius seems the least likely guest for two reasons.
For one, Logarius is basically not there mentally. He's emaciated, he has no duties besides defending the throne and he does so voluntarily. The second reason is that, Iosefka would have absolutely no reason to take the summons from you were it from Logarius. Logarius led the Executioners, who were part of the healing church, which the Choir leads. Unless Logarius was planning on turning on the Executioners (and there's no real evidence that's the case), Iosefka has no reason to take it.
She does, however, have reason if it's from Annalise, the queen of the Vilebloods. The Vilebloods are in direct opposition to the Healing Church and Annalise herself says she is Queen of Cainhurst Castle - this dismisses any suspicion that the Vilebloods are merely being imprisoned there or they're holing up in the castle. So it stands to reason that Iosefka, upon seeing a Cainhurst Summons on a patient in the clinic and being an agent for the Church herself, quickly takes it away because she assumes the sick person is up to some bad shit that could end up ruining what the church is trying to do.
This brings me to the actual point I wanted to talk about: You were summoned to Cainhurst, that much is clear. Why?
As mentioned, Cainhurst is abandoned. Did the queen summon you to save her? Why would you agree to do that? I think a lot of this mystery comes down to the Vileblood Covenant in general. Covenants in this game are fairly useless, but Vileblood's quests are
bafflingly useless. You can give the queen a thousand blood dregs and all you ever get is the gesture for Deep Respect. You can also offer her the Ring of Betrothal, a key item found only in Chalice Dungeons.
"The inhuman beings known as the Great Ones imbued this Ring of Betrothal with some special meaning.
In the age of the Great Ones, wedlock was a blood contract, only permitted to those slated to bear a special child."
You can ask her to marry you - she says no, you're no use to her if you're not out there hunting for blood dregs.
So when I say this bafflingly useless, I mean it. Let's also quickly establish Blood Dregs.
"The Vilebloods of Cainhurst, blood-lusting hunters, see these frightful things in coldblood.
They often appear in the blood of echo fiends, that is to say, the blood of hunters. Queen Annalise partakes in these blood dregs offerings, so that she may one day bear the Child of Blood, the next Vileblood heir."
You may have to squint to see it, but that's, like, blood semen. If the description wasn't enough to make it clear, you're giving her blood dregs in hopes that she gets pregnant and produces an heir for the VIlebloods. Which brings it all back to the question of why you were summoned to Cainhurst in the first place. The easy assumption is that Iosefka took the letter to stop you from doing exactly what you did, killing Logarius and maybe helping to knock up the Queen to produce new vilebloods. But ultimately, isn't that kind of a small concern for a group whose end goal comes that night? Why bother with you at all? That's also so...plain for this mystery. I'm sure there's more to it.
I'm unsure if it's related, but I was thinking today how strange it is that the Upper Cathedral Ward only has one human, the priest with a scythe guarding a doorway. That makes only three living Choir members - Iosefka, the priest, and the man who you met in Bergenwyrth and tried to kill you. I imagine this is significant, if unrelated to your summons, but I wonder what those three people were doing in their locations?
