The Mage War led to the Cataclysm that created the Blasted Lands. A scar upon the land, hundreds of miles of desolation, a barren waste where only abominations grow. Pollution, instability, and the drain and stagnation of the Ley Lines led to the creation of monsters and Dead Zones. The Mage War brought on the destruction of Osterra's great civilization. The end itself was caused by accident, in desperation the Risa Fae shorted out the Ley Lines.
In an effort to stop the Mages they caused a violent fluctuation in the Ley Lines that created magical feedback that cascaded through and reverberated in all of the Ley Lines on the planet. The explosion targeted all of Mages indiscriminately and those connected to the lines at the time perished or were driven mad. The mass extinction of mages caused their advanced civilization to plunge into an apocalyptic Dark Age.
To this day it is very difficult to access magic and the Risa Fae actively dislike magic users.