A Dance with Dragons
When the Dragon’s first conquered the mortal realms they thought that they had the sole possession of Arcane Magic. The conquered mortals practised divine magic granted to them by their Gods. When arcane magic began to manifest itself amongst the mortals, the dragons where shocked and afraid. Here was a power that in theory could match their own, and they went about to extinguish it by killing practitioners wherever they appeared. This only worked somewhat, as more and more began manifesting the talent for magic. What the Dragons did instead was to control the mages by creating the Citadel; a place/organization where mages could be taken, taught the art, and ultimately controlled. A person is taken by the Citadel when they manifest magical ability (even as young children) and taught to harness the power in a way that is deemed appropriate by the Dragon rulers. Magic is corrupting. Some say that this is because infernal powers granted magic to the mortals; others say that mortals are not as in control as much as Dragons. Whatever the case; a mage must always be on his guard for the forces of darkness seek to taint magic users.