The information is obtained from the game, Toukousphere and from the Settei book. Thanks to Kensou77 and Aquagon for translations and for providing the information, which can be found here and here. The info from the Settei book is very complex, so it'll be somewhat simplified here.
I haven't played through Cloche, the third At II reyvateil's Cosmosphere, or any of Ar tonelico III's reyvateil's Cosmospheres, so help and suggestions for the later level themes would be great. (hint, hint) Also, let's try to keep this as non-spoiler as possible, though it probably won't be a problem. Remember the spoiler tags if it's necessary to demonstrate points, correlate characteristics, etc.
About the Cosmosphere
The Cosmosphere is the virtual depiction of a reyvateil's mind, accessed by using a Dive Machine. The Cosmosphere exists for the creation of song magic, made from the reyvateil's emotions. They're obtained by solving the problems in her mind, or Cosmosphere. Each one is unique to the reyvateil, and if it ceases to exist she will die.
A Cosmosphere has approximately 9 levels, and in each level the reyvateil gains songs after being influenced by the diver. In the beginning (Level One), the reyvateil's inner self is weakly influenced and creates weaker songs. As the levels progress she's more strongly influenced and creates stronger songs out of the feelings she has. At level 9, the strongest songs are made from the strongest emotions. Most of the time, reyvateils learn around 15 to 25 songs after completing the Cosmosphere in the course of the game, which is usually a year or two. But, it's extremely dangerous for a diver to go beyond the 9th level, which is usually inaccessible by the Dive Machine. Level 9, the highest level, has the strongest effect on the reyvateil. Beyond it is an area that should never be touched, because doing so could destroy the reyvateil's mind. That area is also called the [Shared Consciousness Field], where the consciousness of all reyvateils meet. If a diver were to enter that area, he could end up influencing other reyvateils as well; reyvateils can also influence each other through this area, though they can't target specifically who they want to influence. As a diver and reyvateil progress through the Cosmosphere, their minds grow stronger-- so, if a diver enters the Shared Consciousness Field, the reyvateil's mind breaks because of the strain of the power in her mind. Because of that the limit of levels one can enter in the Cosmosphere is limited to 9, for the safety of both the reyvateil and the diver.
The Cosmosphere layers are the most superficial in the beginning, and in the later levels, the subconscious thoughts and hidden feelings are revealed. The Cosmosphere is sort of like an onion-- even if peeling the first layers makes you cry, get through to the end to reach your goal! The layers of the Cosmosphere also get more intense later on because of the escalating emotion, and there's a chance the diver could die. In the game, the diver is saved, but when making your Cosmosphere it's possible to have death traps all over, if the reyvateil is extremely hurt or wary.
Completing (the journey through) the Cosmosphere
In the Cosmosphere, the diver helps solve the reyvateil's problems. He talks to her, convinces her of things, urges her to action (or urges her to not act), and acts himself in order to demonstrate to her the answer to her problems. By doing this he influences her, and when she is strongly influenced (at the end of the level, when the problems are solved) a [Paradigm Shift] forms. The Paradigm Shift prepares and allows the diver and the reyvateil to enter the next level... In a sense, the two level up and have access to a stronger area. Because the Paradigm Shift is a manifestation of the influence of the diver on the reyvateil, the reyvateil must enter it by choice in order to safely continue. If forced it can cause instability in the next level and make it harder to complete than it should have been.
If a diver tries to access a higher level than the one he should, he will die (his mind will be absorbed or eroded (causing his mind's collapse) by the reyvateil's, and he will be unable to return to reality). This is because the reyvateil has a stronger consciousness than the diver at that point, so he will be overpowered and unable to influence her, like how a level 5 hero can't damage a level 30 boss monster.
In some cases, the problems a reyvateil has cannot solely be solved by the Diver. In this case, an outside influence is necessary in order for her to have a reassurance of something-- this outside influence can be compared to a weapon or armor the diver can use to help win against the boss, which he could not do without it. Generally, the outside influences can be anything-- a revelation, information, the return of a personal item... Something that has importance to the reyvateil.
Above, we mentioned the dangers of diving past Level 9. However, a reyvateil can sometimes have another level (called Level E), in which the reyvateil is free to do whatever she wishes. This level is likely part of the Shared Consciousness Field, but in-game it has shown no negative side affects, so we can assume it is safe, unlike another level above. Diving past this point is suicidal in most reyvateils, except for a special type in which there is only one, canonically.
Manipulation of the Cosmosphere
Because the Cosmosphere is a representation of the mind, it's possible for a reyvateil to consciously change and manipulate her Cosmosphere. However, it's not something any reyvateil can do. A good example is a Dive Therapist, who is trained to manipulate the first level of her Cosmosphere in order to perform therapeutic sessions with another in a relaxed or preferred environment. In that manipulated Cosmosphere the reyvateil can do whatever she wishes to a reasonable degree. Some examples are fake surroundings, false circumstances, creation of games, false paradigm shifts, representations of real-life people, etc. Dive Therapists are also taught Song Magic to be used for Therapy.
For most untrained reyvateils, it is probably impossible to manipulate the Cosmosphere. For 3rd Generation reyvateils, rigorous training is needed just for the first (the weakest and most superficial) layer. The later levels are even more difficult to manipulate and take a great strain on the mind. Theoretically, it might be possible for the reyvateil to grow mentally ill if she continues to go against her true Cosmosphere and allows someone to advance through her mind without properly accomplishing the levels.
However, for Origin Type reyvateils (the first three reyvateils crafted, also known as the three Goddesses Eolia, Frelia and Tylia), they are free to do whatever they wish with their 'Cosmosphere', because in reality they have none. Their minds are housed in the Binary Field, so they have free reign over everything in the Cosmosphere. The reason for this is because the Cosmosphere concept was introduced after the 'birth' of the three Origins, but to compensate that there are games available to play in the Binary Field, already preset and waiting for use.Even though it's not a true Cosmosphere, obtaining Costumes and Song Magic is still possible. It's also possible to create original scenarios in the Binary Field. However, doing this is dangerous as it's possible to die when in the Field. Some reyvateils whose power nears the Origin reyvateils' can also manipulate their Cosmosphere without much problem for the earlier levels, and can also allow more than one person to dive into them, but because they do have an existing Cosmosphere it is impossible to continue manipulating it without consequence.
When manipulating the Cosmosphere, it can mean either a completely fake area with no hint to the reyvateil's inner mind, or it can be the Cosmosphere with the essential elements still intact, but hidden and manipulated from the natural way of the reyvateil's mind. Either one is impossible to maintain forever throughout the Cosmosphere and can place great strain on her mind.
Cosmosphere Level Themes
In the second game, we learned that most Cosmosphere levels, or layers, go by a theme. These themes are all mostly speculation, except for #3 which is canon, and only apply to most 3rd Generation and Beta Reyvateils' Cosmospheres.
1. Wariness. The reyvateil is reluctant to show herself to the diver, usually by covering her cosmosphere or having a sort of 'protection' around it. It can take the form of a false world, or more mundane barriers similar to a moat around a castle (doesn't impede much, but is still a problem in entering).
2. Self-Depreciation. One of the reyvateil's faults is shown and emphasized, but in a sort of roundabout yet obvious way. This weakness is something they realize about themselves, but don't talk about in daily life.
3. Memory. This level is supposed to be based on memory, so we can assume it takes the form of events that have happened in the past, usually repeatedly.
4. Self-Image. In this level we see the reyvateil's problems with who she is and how she is portrayed. It can impede her from doing what she really wants to do because of the limitations of how she's seen gives her.
5. Goal, Dream, or Wish. This level has two versions. In Ar tonelico I, the reyvateil has something she wants but can't get by herself, because of an outside or inside force. In Ar tonelico II, the theme is pretty much the same, except the 'thing' she wants is the diver's heart. Obviously, she needs consent, but she is also fearful of the love because of an outside or inside force.
These are probably the most accurate ones I have. From here on, there is only analysis from Aurica, Misha, and Luca's Cosmospheres. Because of that, they're lacking in a lot of data... so if you want a better one, you know what to do. ^__^
6. Control. The reyvateil starts gaining power over the diver as the levels progress. This level has two versions. In Ar tonelico I, the reyvateil's love confession is placed here, but because of her rising power she wishes to keep the diver in the Cosmosphere to stay with her forever-- she wants to keep his heart using ploys. It differs from Ar tonelico II because now, she's more powerful, whereas in level five she needs his decision. In Ar tonelico II, the reyvateil also tries to keep the diver in her Cosmosphere because, yes, she's more powerful. In both situations it's a sort of life-or-death decision, but the diver will (probably) live for the next level.
7. [Final Conscience] Fulfillment. This one was a bit vague, so it's probably less accurate than the others. But, in this level, the reyvateil achieves something she wanted for herself, and can be either selfish or for a better cause (usually the former). Also, stated in Ar tonelico I, this level is the [Final Conscience] level, and if this level disappears then the reyvateil's actions will become irrational.
8. Resolution. In this level, the problem from the previous level will be solved and the reyvateil's mind will be calmed at the end. This doesn't mean that she's fine now, but it means the biggest issue (when it comes to mental stability) has been addressed. In Ar tonelico I, the two sides representing her split emotions will collide and destroy the Cosmosphere, but they will join together when brought to their senses to form a new and better world for the reyvateil, showing her healed psyche.
9. Vow. The marriage ceremony takes place in this level, showing the reyvateil's absolute trust in the diver and giving her a strong connection to the tower or server, making her the most powerful she can be. Before it starts, however, the reyvateil reaffirms the diver's convictions to her.
Most reyvateils have towns/inns, a solitary place such as a field or forest, a Boundary Gate/Life Tower, Stonehenge, and a house/castle.
In Sol Ciel, reyvateils' Cosmospheres tend to be unique, individual lands with varying landscapes. In Meta Falss, it appears that most reyvateils' Cosmosphere grounds take the form of some sort of food. The appearance of the Cosmosphere is influenced by the Reyvateil's experiences-- if she has never seen water, she'll likely not have a Cosmosphere based on the ocean. Just like you cannot describe color to a blind person, a reyvateil cannot have unknown things in her Cosmosphere. For that reason, the Cosmosphere takes the form of things she's seen, likes, or is familiar with.
About making a Cosmosphere
The Cosmosphere is the very mind of the reyvateil. It represents her thoughts and feelings. As such, if you want to make one for someone, you have to understand that person. What's her greatest weakness? Her fear? Her wishes? Obviously that's not some trivial 'write it down on her profile information' type of thing, because those are in the soul of a person.
Something I like to do is to 'live' in the character. When you have absolutely nothing to do and are extremely bored, try going back to the earliest memories of the character and imagining everything that happened to them through their eyes. How would she react to seeing her village burn to the ground, everything precious to her in a blazing fire, burning and disappearing from the world? That's something unforgettable. I usually do this at night when trying to fall asleep, but somehow can't. Don't do this just randomly anywhere where there is a lot of distractions, because you can't become the character while surfing for music or watching TV. It needs a sort of drifting state where you can lose who you are and become another.
After that, you can imagine how 'you' would protect your mind, the things 'you' fear and wish for, because of the things that have happened in the past. It's a good way to start in the creation of a Cosmosphere. You don't need to write anything down about her feelings, because usually it just becomes lifeless text that can't be felt. Just remind yourself of that life, and the things 'you' experienced.
Here's a method by Chaude, which looks like it'll work even better.
Chaude wrote:Another way to create a Cosmoshpere is a step-by-step method from personality to Red and Blue magic to the individual Cosmosphere level.
1: As mentioned already, spend a good amount of time to reflect on how the character reacts to others and herself (from being happy to sad to angry), and next, develop Red and Blue magic from there.
Example: With my character Kaylan, part of her starting personality is kindness and sincerity, yet shy and mysterious. This develops her Hallowed Strike Arts that's based on Light and Darkness.
2: Once all of the Red and Blue magic spells are made and assigned to each Cosmosphere level, spells that are assigned to each specific level become the characters that aids and/or go against the diver. In addition, those characters, based off of those spells, create the level itself (sometimes by their attribute, their emotion, etc.) and reflects a specific personality trait of that Reyvateil.
Example: Kaylan's Shadow Flare and Knight magic created her 3rd Cosmosphere, named "Forgiveness in Darkness." With a dark-based attack and a knight figure, the end result I thought of for the area was a swamp. From there, I selected what personality trait did I want Kaylan to resolve, in which case I selected her inability to forgive herself for her weaknesses.
3: Henceforth, what obstacle(s) do you want to present to either the diver or the Reyvateil, or both, to achieve the Reyvateil's understanding of herself and experience a paradigm shift.
Example: Because the personality trait I selected dealt with her inability to forgive herself for her weaknesses, I felt Kaylan had to be doing something that she couldn't do herself. It had to be something that she felt she knew she can be able to do, but somehow can't complete it. I used a zombie as an obstacle (zombie created by her more deeper emotions, yet less fierce at this early level). Zombies are thought of to be easy to be killed (immediate experiences from Valkyrie Profile). When I pit Kaylan against this seemingly easy enemy, I increased the difficulty of the obstacle to reflect the personality trait, giving the zombie protection from normal attacks and holy- and fire-based attacks that she has as her arsenal at this time. This is when the resolution brought by the diver comes, understanding, and the creation of a paradigm shift.
There are a lot of ways to create the scenario, obstacle, and resolution. I'll admit this works in theory, so if there's any corrections, I thank you for your input . I hope this was helpful.