Mistvale is at the center of the map and is unable to be accessed at this time! Here's the bit of lore from the Wiki.
Mistvale occupied the center region of Loria, during the wars their leader, Korvo, transformed the land into a sanctuary. The youngest sibling's mind was twisted by Chaos himself and in time the paradise turned into a sick, wicked land. When his siblings returned and discovered his corruption with he help of the Creators he and Chaos was defeated and inprisoned in Lake Veridia. His last words warned us all that he would return, stronger than ever.
