While the nations of Erebus recovered from the harsh era of stasis during the Age of Ice, Ceridwen answered Mulcarns appeal to the evil gods as he passed through her indefinite vault after his defeat by Kylorin. Determined to avenge her former protégé, she invoked a cataclysmic event, creating a interdimensional rift that partially absorbed Creation.
Sentient souls are caught in this rift. They experience seemingly immortal lives in a dreamscape called Somnium.
Eventually, substance taken from Erebus will form a reflection of Erebus, Vesperus. Dagda, guardian of the Compact, intervenes in this process by creating a separate vault, Nemesis, to salvage and protect what Ceridwen took from Creation. Some day the Rift will release all souls and they will be guided to Vesperus through Nemesis, and find their new mortal home.