DVA
The DVA, or the Dimensional Variance Accelerator, is the brainchild of SEBEC and the particular efforts of former CEO Takahisa Kandori along with the researchers Dr. Nikolai and Setsuko Sonomura, the latter two of whom still work with SEBEC. Their goal was to create a weapon; in a sense, they may have succeeded.
In the strictest terms, what the DVA does is create a pocket dimension, carved out of the folds of reality. This reality is shaped and directed by the mind of the individual within the machine--for that is the secret of the system. A human needs to be present within the machine for it to function, and not just any sort of human will do. Only certain people are compatible with the DVA. Of course, a machine of such great power does inflict certain stresses upon the psyche. Some people... break, compatible or not.
Experiments on the first-isolated compatible subject, Maki Sonomura, eventually resulted in the creation of Mikage-cho, which continues to linger on even without the DVA's direct influence. Later, the machine fell into the hands of Kandori himself, who attempted to use it to become a god, only to meet his end at the hands of those who defied him.
No longer in the hands of either the now-deceased Kandori or the NWO, the fate and current location of the machine is a mystery.
The Machine
Even within the remains of Kandori's SEBEC, little documentation about the system has been unearthed. What has been gleaned is that it should, quite frankly, not be able to work, or at least definitely not do what it has been demonstratively been show to be capable of doing.
This is not far from the truth. The DVA /shouldn't/ work, and yet it does. Whether this is a function of the machine's interplay with a human psyche or if it draws upon some darker, alternate source to power its capabilities is uncertain, even for those who have sat in the heart of the DVA themselves.
Functionality
Maki Sonomura was the primary subject for the DVA for most of its existence, but she is by no means the only one who can make use of the machine's particular abilities. Anyone who meets the base requirement will do.
The base requirement for the use of DVA is a living body that possesses the quality of 'compatibility'. Compatibility is fairly straightforward: most characters with a Persona or Shadow possess the something 'extra' that the DVA requires to create a pocket dimension, but there are some exceptions where it simply doesn't work for a given character at all. For example, Kandori was unable to interface with the DVA directly. This is always determined by the player of a particular character.
Once inside the machine, the character can no longer interact with the outside world until they either escape the DVA or manage to leave by their own volition. The latter can be tricky; the grip of a self-crafted dream world is particularly seductive, and entrance into the DVA typically causes most characters to fall unconscious while within it. This is no barrier to operating the machine, of course: some of the mechanisms of the DVA are intuitive even unconsciously. In fact, it's purposely set up to function with an unconscious mind. These mechanisms include all the basics for world creation. However, finer control is only possible with experience... and the ability to remain conscious and in direct and total control of the machine.
The stress of the machine can cause a partial or complete shattering of the psyche. This is also determined to happen or not by the player of the character, though it is far more likely to occur the more conscious control the character attempts to assert over the machine. The DVA is not a gentle or kind machine. It does what it does, and it does it without concern for what might happen to the humans serving as its core. For those who experience a shattering, complete or not, aspects of themselves appear within the pocket dimension they create, often representing a certain side of themselves. For example, Maki Sonomura generated three different selves within Mikage-cho: a representation of her super-ego, Mai, who manifested as a little girl in white; a representation of her id, Aki, who manifested as a little girl in black; and an ideal version of herself, a teenage girl who was exactly who she wanted to be, a representation of her ego. Other variations on this theme are certainly possible.
The Pocket Dimension
The pocket dimension generated by the DVA is strongly influenced by the particular character's psyche, taking the form of a mirror image of the location--typically no larger than a city ward--where the DVA was activated, though distorted and including the elements important to the character prominently. However, they also integrate aspects of the dark side of the character's psyche, which may take many forms. For example, when Maki Sonomura used the DVA, a mirror image of Lunarvale was created, with one side more or less resembling the city as it was normally (if with some key differences) while the other side took the form of a post-apocalyptic landscape.
Demons rather than Shadows always inhabit the alternate dimension, and can pose a threat to travelers. Their specific presence seems to have something to do with the functionality of the DVA.
Entering the alternate dimension can be accomplished in two ways. Characters can be dragged into the dimension when the DVA is first activated, if they are close enough to the machine. Secondly, transient portals open up in the analogous area to the pocket dimension, through which characters can enter willingly... or not.
The character within the DVA is able to interact with the dimension they created by ways of an idealized avatar of themselves. Their personal avatar does not have any more power than the character usually possesses on its own, since most of the character's psyche is caught up in maintaining the world. If they have experienced a fracture of their psyche, they may generate a variety of avatars, as noted in the previous section, which will roam their ideal world. They may individually have less, due to their splintered state. Certain characters' avatars and selves may have power within their world of a degree more akin to a demi-god, but this is typically associated with long-term exposure with the DVA. Characters with this capability are determined on a case-by-case business by admin.
Characters who are injured or even die within the DVA-created world will carry those over to the real world however they exit. This means that all injuries are effectively real injuries, and all deaths are permanent.
Ending the Dream
Not everyone who uses the DVA has control over it. Rather, the machine rides them. Without the ability to control it, the DVA continues to maintain the pocket reality. For these characters, they absolutely need someone to come and rescue them from the core. However, extracting someone from the core without killing them is a tricky procedure.
Two options are available to would-be rescuers. First of all, violence--with care--can be sufficient to damage the machine enough to shut down its operation and allow for the extraction of the character within it. The other option is to reach the character within the DVA by way of their avatar. Control of the DVA, for most characters, is not a conscious affair, and for them completely managing the machine isn't even possible. However, even they could, if prompted, understand how to shut down the machine from the inside. The only problem is that they aren't aware of where they even are, and thus are completely at the mercy of the machine.
The trick is in drawing attention to that fact. Once the character, via their avatar form, is made aware that they are merely 'dreaming', the option is now open to try to force the machine to stop. However, there's always the possibility they won't want it to stop. It is for them, after all, a dream world.
Barring intervention from a more powerful entity, the dreamworld fades utterly from existence once the individual stops the DVA or the machine is forced into a shutdown.
