Okay this is edited version:
The wiki is not really the most reliable of sources, and it a good quick reference and not wholly inaccurate but it only does so much good as a reference and as the Valley of Screams made it's debut in Memories of Nobody, I watched it to get a feel for whats being debated and what has been stated so far.
These descriptions are taken from the Wiki and will be important to making my points.
General overview: A Valley of Screams is a dimension that forms between the Human World and the Soul Society, stemmed from the Dangai.
- Manga: Valleys of Screams are pockets of space, varying drastically in size, that are composed of souls ejected from the reincarnation cycle and reside in the space known as the Garganta. Despite the fact that the Reiatsu in the Garganta is incredibly unstable, to the point where no one can move through it if they do not constantly release their own Reiatsu to create footholds, the Valleys of Screams are able to exist as dimensions of Reishi for an unknown reason; Yoruichi Shihōin theorizes that they are able to do so because the very structure of their Reishi is different from that of normal Reishi.
- Movie: There is only one Valley of Screams, and its appearance is a regular occurrence that happens naturally due to souls getting lost trying to get to Soul Society; as such, it can only be accessed from the Human World. The lost souls that create it are known as Blanks.
- Garganta: A Garganta is a spiritual pathway connecting Hueco Mundo to other worlds. Besides the Human World and Soul Society, it can open the gates of the Dangai. A turbulence of Reishi blows within Garganta. To move through it, travelers must create footholds using the Reishi.
- Dangai: The Dangai (Parsing World), also known as the Precipice World, is the dimension between Soul Society and the Human World, separated from space and time. The Dangai was originally both a penal colony and a passage to the Human World. The Kōryü (Wresting Flow) and the Kōtotsu (Wresting-Surge) are remnants of its time as a penal colony, they also act as a means of defense against unwanted intruders. The Dangai is an isolated space which is surrounded by numerous stacked-up layers of time's current, resulting in it being a place where the density of time within it to be extremely high when compared to other exterior dimensions.The Dangai was an integral plot-device for the first Bleach feature length film, Bleach: Memories of Nobody. It inadvertently spawned the Valley of Screams, and was revealed to play a role in the creation of Blanks.
The Wiki description above for the Movie's VoS generalizes the Movies events without having actually covered the details of the matter, as from just watching the movie the first 1 minute and 22 seconds,
https://youtu.be/VKNd3HheTMw?t=15
Are about the 12 Dvision has monitoring an anomaly with this gradually expanding dimension and a team from the Stealth Force has been dispatched to investigate, and they were accessing it from the Dangai and Rin Tsubokura noted how they were 10 seconds away from entering the dimensional zone (VoS) and set up communications with them only to hear how their exit closed, that the dimension had now become inaccessible and that they got caught up in the Restricted Current, and died.
At the link provided from 18:14 to 19:18 Kisuke (then Toshiro) begins to explain the situation with this new dimension,
https://youtu.be/esFxEL5TBqw?t=1094
About the relation between Earth and the Soul Society and the Dangai's role in keeping the two from colliding. Since the dimension had become inaccessible from the Dangai and there was no entrance to it from the S.S they were investigating strange influxes of spiritual waves coming from the World of the Living, which was the only place that had direct access to this expanding dimension, it was just a matter of locating it.
Now the Wiki's general overview and the manga's description of a Valley of Screams and the Dangai's role in its creation, borrowed from the Wiki:
- The Dangai was an integral plot-device for the first Bleach feature length film, Bleach: Memories of Nobody. It inadvertently spawned the Valley of Screams, and was revealed to play a role in the creation of Blanks.
- A Valley of Screams is a dimension that forms between the Human World and the Soul Society, stemmed from the Dangai.
- Valleys of Screams are pockets of space, varying drastically in size, that are composed of souls ejected from the reincarnation cycle and reside in the space known as the Garganta. Despite the fact that the Reiatsu in the Garganta is incredibly unstable, to the point where no one can move through it if they do not constantly release their own Reiatsu to create footholds, the Valleys of Screams are able to exist as dimensions of Reishi for an unknown reason; Yoruichi Shihōin theorizes that they are able to do so because the very structure of their Reishi is different from that of normal Reishi.
The Soul Society through the 12th Division first noticed the anomaly from within the Dangai and that is where the Shinigami of the Stealth Force initially tried to enter it to investigate the reason for its expansion, until shut closed on them. Just like it says for the Valley of Screams, this growing dimension was first noticed in the place from which the Valley of Screams originates, the Dangai, but the Valley of Screams occupies the space known as the Garganta so if that is the case then using this wiki description of a Garganta as reference.
"A Garganta is a spiritual pathway connecting Hueco Mundo to other worlds. Besides the Human World and Soul Society, it can open the gates of the Dangai. A turbulence of Reishi blows within Garganta. To move through it, travelers must create footholds using the Reishi."
So if the Valleys of Screams occupy the Garganta's space, and Garganta's can open into the Dangai it can be inferred that the Garganta is a space that lies just outside the Dangai, and is perhaps kinda like a dump for everything the Kōtotsu the "Cleaner" catches and discards which could explain the unstable nature of the Garganta's reishi.
That brings us to Urahara's second explanation from 19:29 to 21:04 and the expansion upon it by Ganryu and Mayuri from 55:35 to 57:38,
https://youtu.be/esFxEL5TBqw?t=1169
https://youtu.be/esFxEL5TBqw?t=3365
When Ichigo described the Blanks, Kisuke and Toshiro recognized them as what they are and knew that must mean the mysterious problem dimension must be a Valley of Screams. Kisuke described how a Valley of Screams forms from souls that became separated from Transmigration or the Cycle of Reincarnation having lost their way in the Dangai which is a fact missed in the movie description of the Valley of Screams on the Wiki, but played straight in the description in the Manga. That this collection of lost souls gather into a Valley of Screams where the Souls separate into Memory (Shinenju) and Energy (Blanks/Valley of Screams).
Kisuke had described that the appearance of a Valley of Screams, the context suggesting that has been more than one as opposed to how the Wiki's description for the Movie:
- Movie: There is only one Valley of Screams, and its appearance is a regular occurrence that happens naturally due to souls getting lost trying to get to Soul Society; as such, it can only be accessed from the Human World. The lost souls that create it are known as Blanks.
He went on to say that the Valley of Screams is in of itself not a cause for concern since it is a natural and common phenomena, but the fact that this one has connected the WoL and the S.S, and that is what is not a natural occurrence and that someone must be messing around with it to cause this problem in the first place.
The fact is we already know from recent events in the Manga and from the Dark Clans ability to draw on the VoS for power that a Valley of Screams can be manipulated with right knowledge and ability. Fullbringers can manipulate the "soul" or spiritual energies present all matter, and they can even go so far as to alter certain object because of a closeness to that object, being that from close and contact with it they have imprinted themselves onto it on a more personal level than they would with say, the sidewalk or a lamp post that comes into contact with many different people on a daily basis, but that closeness or affinity allows them to pull out the object's soul and boost it with their own, transforming it in the process.
Now a Blank and therefore a Valley of Screams is composed of raw undiluted Spiritual energies that lack memories and connections so it would not be unreasonable to assume a Fullbringer who can draw on spiritual energy and whose powers are based upon personal connections could be able to "pull" on a VoS with ease and basically do what Yukio and Riruka did at Kisuke's behest.
Kisuke used this Fullbrought Valley of Screams as a method from which to travel undetected to and within the Royal Realm, now The Dark Clan who resided within the Valley of Screams and relied on its power if they could shut it off from within the Dangai it is likely they could made sure it's only entrance was within the World of the Living which makes perfect sense since their goal is to capture the Shinenju (Senna) who is in the World of the Living and bring her to the center of the VoS to basically destroy the world
https://youtu.be/esFxEL5TBqw?t=5212
Rukia explains that as the Blanks energies continue to dissipate all memories of Senna in of herself will fade, due to being non-being but it does not mean everything else disappears as well. As there were many who did not come into contact with Senna but still experienced the events of the movie and knowledge of Shinneju, Blanks, and VoS still exist along with the fact that they would technically remember everything else but the specifics of Shinenju Senna (though Ichigo might).
The very fact that Ichigo referenced going to a Valley of Screams and the image provided is what it looked like in the movie, if the events were not on some level canonical there would little reason for him to reference having gone to a formerly non-canon dimension based around non-canonical events. What possible reason would he go to one if not for the events shown in the movie?
I hope this is better than before.
