The world of Rêve is a dragons' dream. The dragons, fabulous creatures, are asleep and each of them dreams a creature ; but at the same time, all of them dream the world. When a creature dies, his dragon awakes, but as the creature is also dreamt by the other dragons, its body remains.
This is a metaphor of the role-playing game itself : when players gather to play, they imagine - dream - together an adventure, and each player imagines his own character.
As well as different stories often interfere (e.g. a player plays different games in the same week), the different dreams (worlds, universe) can interfere; there are rips between them, and the character can go to a different world sometimes without noticing it! Strange creatures can also come to the present dream.
Just like a sleeper has only partial control over his dreams, why would we have nightmares otherwise ? the dragons do not completely control their creatures and worlds. The dreamed creatures have the possibility to modify the dream (the world) itself ; this is the source of magic, highdreaming.
The life of a character is fuzzy between the game sessions ; the player only has little ideas of what happens to his creature. In the same way, characters of Rêve de Dragon sometimes experience a gris-rêve (greydreaming): they suddenly realise that they are somewhere with companions, but only have limited memories of what happened the days before. But what happened can be the key of the current situation...
When a character dies, his dragon wakes up and then falls asleep again ; at the same time, the character wakes up in a new dream, a new life. This means that the character is recreated with the same abilities, but a different past, a different job, different skills, a different name. The player thus plays the same character again. well, not exactly the same : the character is not a newborn, he is already adult, just coming from another dream.
The "sum" of all these incarnations are the archetype of the character. When the character is himself sleeping, he can remember his past incarnations, and thus learn skills he never practiced nor studied. These memories of a past life can also be the key of the adventure..."
Source: Wikipedia, "Rêve_de_Dragon," available under the CC-BY-SA License.