Born Human, Part 1 by Viola Grace

Human at birth, troll by design. Destiny had a sense of humour and made her something else.

Habel is beyond excited. She has reached her changing day. Turning twenty-one brings new life, new responsibilities, and a new body. She will finally be a full-fledged member of her community—a troll.
Since the great cataclysm, every person was born in human form and transformed into their adult form the day they turned twenty-one. Habel is no different. She was born to a set of troll parents, raised in troll society, and watched her siblings transform from unchanged to trolls.
Tonight it is her turn, but while she transforms, things do not go precisely to plan.