Xylos's Return

The Heart of Xylos returned during the Chaos Wars, which was what caused the Cataclysm. The various types of radiation and magic interacted with the technology and magic being used during the battles, corrupting both. This caused and/or made the wild magic storms worse.   The corruption of the Heart opened many Rifts, caused many magic storms, D-shifts, and even caused multiple Planes to overlap in Teranik (this caused many deaths and mutations from both planes). It caused the creation of the Skylands by altering the local gravity, changing the Planar laws, and various other things. There were   Some magic items had access to the Plane of Water, such as fountains that had a safety feature so they wouldn't overflow. This function broke and caused the The Flooding of Aquatica. In some areas, pocket dimensions were created. You could be walking in a desert, and in the next step, you could be in the jungle or underwater.   One thing that changed many lives was the merging of animals and humanoids, or accelerated evolution, of many animals. This is how the animal-folk were created. Some are permanently, changeable, or temporary.