History of Magic
The history of magic is lost to most of the world since the advent of The Veil Treaty. However the details remaining from that period included powerful mages who masqueraded as gods and twisted magic users who turned into demons to prey on humanity. From both of these sides came a wide variety of plant and animal life that was twisted or reshaped into new forms: Dragons, Gryphons, etc.
Even more vague tales exist predating recorded history that tell of the origins of magic and of incredibly alien entities that ruled the world. How or why exactly these creatures 'went away' is unknown, but many magical historians argue about the reasons. The leading theories involve the rise of human magicians who could fight back against these creatures.
After the Treaty the magical world continued under the watchful eyes of the Mages Council. They enforce the break between mundane and magical using the Enforcers Guild, who are the only mages allowed individual passage between the sides of the veil. The Magical Research Unit also sometimes is allowed to go on expeditions to search for magical creatures hidden in strange corners of the mundane world to bring them to the magical side of the veil. That said mundanes and even mages, sometimes end up crossing the Veil 'by accident' at weak points.