The Great Cataclysm is the war between both Avalon and Shadowheart. Both entities of light and darkness fought to destroy one another. Their creation and origins are a mystery to this day.
Both gods fought over and over, each fight springing another universe to life. Hundreds upon hundreds of battles followed until eventually an entire multiverse was created.
After countless years each god began to lose power. In order to protect themselves, they retreated to dimensions of their own creation to sleep. It is said one day they'll return, continuing their endless struggle.