In the Magic Unleashed series, one of which is fire. Chaos is one of the darker, more dangerous forms of magic. Fire is the servant of chaos, and forms an important aspect of chaos rituals. Wizards who employ fire magic accomplish infernal feats of transformation and destruction.
Fire is naturally destructive. Chaos magic enhances that destructive power to epic proportions. Chaos can enhance people, animals, and people in many ways. Physically, emotionally, and in terms of raw power, few living things can withstand fire magic.
Using any form of magic changes a wizard and their familiars over time. Rage is a key aspect of fire magic, but embracing fire repeatedly leaves even the most resilient wizard prone to bouts of corrosive anger. Blinding rage becomes more and more prevalent as a wizard draws on more and more chaos. Eventually, the person that was is consumed by chaos entirely.
Only careful use of fire magic, and an insulation from the rage that accompanies it can stave off this effect. Fire wizards instinctively know this, but often forget or ignore the insulating practice in the quest for more power. Power through chaos is obtainable, but the cost is an intimate loss of self.