"Astral World" is episode 201 of the Berserk manga series.
Summary[]
Flora says that she has been awaiting the arrival of the Branded Guts and Casca. Her being aware of the Brand makes Guts suspect Flora of being an Apostle, but he decides against it based on the fact that the pain he feels in his Brand when around her is different from the pain that an Apostle evokes. Before he can further question Flora, however, she announces that the problem Morgan has come to inform her of is of the utmost priority.
Morgan confirms that trolls have been attacking Enoch Village, and Flora becomes sullen. She informs the group standing before her that trolls originate from a place known as the Astral world and are rarely, if ever, seen by humans. She turns back to Morgan and sadly tells him that she cannot personally help his village, as she admits she is simply too old to be effective against the trolls. Isidro insensitively points out that Flora's words suggest that she is dying, but this seems to offend everyone but Flora herself, who admits that this is the case.
Fearing that the Beast of Darkness would make him abuse Casca, Guts jumps at the news that its influence can be suppressed.
To appease Morgan, Flora tells him that she intends to send Schierke to Enoch Village in her stead, claiming that the girl's training must be put to serious practice. Isidro teases Schierke when she shows signs of nervousness. Flora then requests that Guts and his entire group join Schierke to provide assistance. Guts denies her request, claiming that his own journey is too important to even temporarily abandon. In an attempt to persuade him, Flora offers Guts to provide him with a talisman (which Serpico tells Isidro is essentially a charm) in exchange for helping Schierke. It is Flora's explaining of what a talisman is that earns her the entirety of Guts' attention - she says that the talisman acts as a sort of shield to prevent the essence of Guts and Casca's Brands from calling out to evil beings, essentially allowing Guts the ability to sleep at night without needing to fear an attack by spirits or being possessed. Guts' mind immediately wanders to the time when the Beast of Darkness took over his mind and nearly made him rape Casca. The talisman would allow Guts to be free of any such thing happening again.
He looks back at Casca, who shrinks behind Farnese. After a moment's consideration, Guts accepts Flora's offer to help Schierke in exchange for the talisman. With the negotiations complete, Flora asks Schierke to prepare meals and baths for everyone, announcing the she will let them spend the night in her mansion without fear of being attacked by spirits or Apostles.
Flora and Schierke explain the true nature of the world.
During dinner, Guts finds the opportunity to ask Flora what she meant by her waiting for Guts and Casca to arrive. The old witch explains that a friend from the Astral world had sent her an oracle foretelling of Guts and Casca's arrival. Before Guts can ask about the oracle, Isidro butts in, demanding an explanation for the term "Astral". Flora explains that the Astral world is, in essence, the realm in which the dead reside, and that close proximity to Guts' Brand of Sacrifice has allowed Isidro, Serpico and Farnese to perceive and interact with spirits, which no regular people can do.
Schierke elaborates, diving into her own explanation. She reveals that the universe consists of three partially overlapped worlds. There is the mortal plane, in which humans reside. This intersects with the Astral plane, in which more fantastical beings like elves, trolls and dead spirits exist. Finally, there is the world of Ideas, from which derives all existence.
Schierke continues in saying that, long ago, many humans were capable of perceiving the beings that exist in the Astral realm, but the spread of the Holy See's doctrine has altered people's beliefs, effectively further separating the mortal and Astral planes. Puck realizes that this explains why Farnese couldn't see him during their first few encounters.
Isidro decides that the simple solution to getting rid of the trolls which plague Enoch Village is to convince every living human that the Astral world does not exist, thereby completely severing the mortal and Astral planes, but Schierke rejects his theory due to the fact that all humans are aware of the Astral world's existence in their subconscious, making it impossible to convince humans that it doesn't exist. Flora takes the explanation from here, saying that the thin overlap which exists between the mortal and Astral realms is called the Interstice, where recently deceased souls reside. As they come to terms with their own deaths, these spirits gradually move into the deeper parts of the Astral plane until they come into contact with the world of Ideas, whereupon they cannot return.
Flora ends her lecture here, having just provided the fundamental information required when attempting to learn magic.