Cerebral reality (CR) is a technology that was invented in PS 12,784 on Damta.
Cerebral reality is an improvement on virtual reality. A person will go to a CR center and see a tiger, or a dragon, or an abomhiz, or a spear, or a sword, or a tank, or a palm tree, or a treadmill, or a river, or a dune, or a mountain, or whatever, but it's not projected by VR technology, the vision is actually coming from her/his brain. A person's visions are fed to her/him and the other people in the CR center by a dreamstream attached to her/his head, coming from a drug called metechin in English (from the Greek root for "share"). Such a shared vision is called a metecheidon. The metechin is stored in a metpump on the ground, and several people sit or stand around it in a circular chair called a puntchair (because it's split radially like the punt in a bottle) to enjoy their metecheida. The field of vision around you in which your metecheidon appears is called your dreamfield.
As the people hang around in the CR center on their puntchair, they can share an adventure. They can ride through a river that leads to the underworld, passing through their dreamfields. Seigo can save Conchita from a three-headed monster, or Ingrid can catch Paolo as he feels as if he's falling from the balcony of an arcology tower. Carly can see hundreds of fans of diverse genders, races, and ages listen to her in a concert and hound her for autographs, or Geoff can go through a herd of abomhiz and hunt them in the savannahs of ancient Damta.
Before the people partake in their metecheidon, they each choose where they'll be and what role they are going to take on in the vision. In the arcology balcony example above, Paolo would choose to be atop the balcony and fall, while Ingrid would choose to be the savior who is standing at the bottom. The other dreamers would choose other, ancillary roles, each with its own part in the entire adventure.