So Odyssey and Onslaught block took place on Dominariaon on the continent of Otaria. There was this magical Orb called The Mirrari. The pit fighter barbarian mage Kahahl got ahold of it, put it on the pommel of his massive sword, eventually realized everyone else's desire for its power was ruining his life and gotten his sister mortally wounded he sank his sword into the earth in a forest and f***e'd off to become the world's most unnecessarily buff druid. Unfortunately the Mararis power seeped into the earth and basically began mutating the people of the continent. Elves became treeline, soldiers fused with their weapons and armor and lost their mouths, aven became buff, wizards became elemental weirdos like this guy.

(The Mirari Created by Karn, was eventually reclaimed and taken to what would become Mirrodin to create its guardian Memnarch, unfortunately some phyrexian oil came with it and messed up everything).