[MultiPigeon]

I wanted to read through the entire thread before posting my theories but I gave up half-way trough.

Anyway

Spoiler for Here are my thoughts about the 'new witch':

My theory is that the birth of Eva-Beatrice is a metaphor for the birth of a new killing intent.
It means that since the first twilight in episode 3, what ever killed in episode 1 & 2 was stopped or seriously halted. Things that point to this is the lack of any magic circles since the first twilight.
I claim that during episode 3, there were two groups of murderers. The first group is the Beatrice group, the killers och episode 1 & 2, and the first twilight of episode 3. The second group is the Eva-Beatrice group. The B-group kills because of the epitath and the E-group kills because of greed.
The connection between the second twilight and the death of Rosa & Maria was an accident. E-group killed them so that they would be the only ones that knew of the gold. By coincident, Rosa dn Maria fitted the role as sacrifice for the second twilight.

Spoiler for Here is my theory for why the deaths are random:

13 must die to complete the cermony. 18 people are on this island. Thus, 5 people will be left alive. However, if Ange wasn't sick, they would be 19 people on the island. My theory says that that there are 6 persons operating together to kill according to the epitath. But since Ange is missing, one of the epitath murders must also be killed to complete the cermony. According to this theory, 6 people aim to murder as in the epitath but at the same time aim to survive thus mostly breaking ther co-operation, creating a situation where the murders happen randomly.

Spoiler for Theory behind the death made 'impossible' because of red text:

Eva-Beatrice claims that the 15 persons are dead by counting up all their names. But if I remember right, she never said that there were 15 dead people on the island. This leaves me with the theory of a doppelganger. If a person named Ingrid kills Rosa takes her identity before coming to the island, Eva-Beatrice can claim that Rosa is dead while Ingrid is still walking around and could kill Nanjo. This isn't of course limited to one person.

I don't feel like I have a complete theory for what's happening. I love the story but I don't find myself as much of a mystery solver. Thus, by posting my small theories that might only cover up a bit of the mystery, I hope to give some new ideas to the persons that are trying really hard to solve the mystery.