The Tunnel of Dreams

The Tunnel of Dreams usually only first opens inside of a horrible nightmare. What happens in the nightmare doesn't appear to matter much, but no matter the case the nightmare has been described by some to put the souls who are screaming and rotting in Hell to shame. Once the Tunnel opens, the person it opened for can access it at any time they wish ... from inside the Conscious Self. If that person strays too far away from the Tunnel while in The Dreamscape, the tunnel will collapse and strand them there, unable to open it and return to the Conscious Self.

Appearance and Behavior

When the Tunnel of Dreams first opens, the person it opened for is taken directly through it. Usually they don't notice anything has happened until suddenly the nightmare stops. From inside The Dreamscape, the person can look back through the Tunnel into their nightmare as though the Tunnel were a giant window, hundreds of feet tall and hundreds of feet wide. Creatures and animals that manifested in the nightmare may continue to roam around, possibly confused at the sudden disappearance of the nightmare's own creator, but they aren't able to traverse the Tunnel of Dreams.
Collapse isn't too much an eventful process. When the person moves too far away from the Tunnel, the Tunnel simply just disappears without any sort of sign that it was ever even there to begin with.

"It's possible that this isn't the same one that brought any of us here. If that's the case we can't be all that sure of what would happen were we to go through it."

— Ayaka

"But we say 'The Tunnel of Dreams,' right? That would mean it’s the only one."

— Futureman

"We don't know if it's a singular object or something that is unique to each individual person. Everyone just kinda agreed to say The and call it a day."

— Ayaka

There are two theories among The Dreamscape's inhabitants on what might happen when one traverses the Tunnel of Dreams that didn't open in their own nightmare. The first theory simply states that the Tunnel rejects them and they pass through it as though it wasn't even there. The second theory states that they re-enter the Conscious Self through the nightmare that opened the Tunnel, although whether they return to themselves in their own place and time or remain in the place and time that the Tunnel opened is not expanded upon.