In my universe, unrestrained use of magic is dangerous both for the unpredictable effect arcane energy has on an environment, but also because of a… fun little wrinkle in how it effects living creatures of sufficient sapience.
See, magic is always seeking to fill a container- be it a gem, a mana pool, or a person. It changes and adapts that container to those needs unconsciously- a mana pool becomes crystalline and heavily charged with arcane energy over time like one would expect pool tiles to crust over, a gem grows facets and faces, and a person- well, arcane energy will adapt a person to its needs if present in their body in sufficient amounts, and it will do this by making them the sort of critter most adapted to storing large amounts of arcane energy- a dragon.
The Curse of Scales, as it is known, is dangerous, coming in stages. A person will begin to grow scales across their body, their eyes will turn reptilian, their teeth will sharpen, then, when they reach the tipping point, a few things might happen:
- They die, excess magic spilling from their body, usually explosively.
- They become a horrific, mindless chimaera, bereft of sense and a danger to everyone around them.
- Or, they will undergo a rapid, irreversible, and sudden transformation into a dragon. Though this is the least bad of the outcomes, and many mages can even push for this result in themselves and others, dragons lose much of their old self over time, and don’t really retain much of who they were without great effort.
Responses to this eventuality range from place to place; magic and mages are too valuable to not utilize, and while many places do have provisions for victims of the curse in their laws, others, seeing the first two outcomes as more likely, will kill mages at risk of turning instead of risking it.
Needless to say… it’s a controversial and persistent problem in my setting.
And… golly, y’know, Rose fought Callie in an experimental and dangerous aircraft that was absolutely drowning in unstable arcane tech called the XFA-09 Fafnir- Weird that she turned out fine, huh?