Mystical, the Tiefling Barbarian (Path of Wild Magic)

Mysti knew from a young age that she was destined to be a wizard some day. She had an undescribable magic within her that she tried learning to hone, she'd studied up on all the spells she could, and she even spent hours practicing!

Sure, none of the spells ever worked, but every wizard experienced blunders from time to time, right? And besides, maybe she was just procrastinating too much for her training to be effective.

There was just one problem; contrary to what Mysti believed, she wasn't a wizard at all, and her magic could never be honed. It was the magic of the wilderness, a thing that came and went as it pleased. She was, by all means, a barbarian.

One thing she did notice, however, is that her magic was strongest when her rage took over, when she could feel the lightning soar throughout her body. All sorts of unpredictable things happened when she was upset, to the point where she was afraid to let her joyful demeanor slip for even a second.

From there, the fear of hurting someone was far more prevalent than the desire to practice, so when she raged for the first time as a teenager, she stopped practicing right afterward. This was the origin of her starting to mask her every emotion.

But she couldn't hold it in forever, and when she finally did unmask the rage she'd been holding in, the repressed power was strong enough to give her lightning-shaped scars for life.

She ran away from her old house out of embarrassment for letting her "wizardly" magic go amok like that, and since then, she's been looking for a relaxed place to live out the rest of her life and trying to not work herself to (literal) death.