Rizan was an ice planet colonised by humans. They created several settlements.
By the time Erimem and Ibrahim Hadmani visited, the locals had been in seclusion for a very long time and were hostile to off-worlders. Ibrahim accidentally changed Rizan's future when he was eaten by Snow Wolves. Before his interference the wolves would have eaten a potentially great leader, but in the new timeline this leader led Rizan into an age of prosperity. Erimem went back in time to before Ibrahim's death and tried to prevent it, but Ibrahim was killed in a different way. Erimem made many more attempts, but every time Ibrahim died. She eventually travelled to before they had gone to Rizan and diverted them to a different planet. This corrected Rizan's history and the colonists stayed in a dark age for a few more centuries. (PROSE: The Snow Wolves)
Erimem's grandfather later used Rizan as an example why Erimem should not change time too much. (PROSE: Echoes)