Fire is forbidden to mages, when Dekor sees the fire he falls to the lust of the flame. The way of the warlock is a path to darkness, not one for a graduate mage to even consider.
"This will give you energy, it will also contain your lust for the flame. You must let your heart decide the path you will walk. Do not let anyone tell you fire is evil. Evil is in the heart, not the hand." Aunt Endor.