She's a fusion of two beings—a human named Shakuyaku and a golem called Kagan. Once they made peace with each other, they adopted the name Shakugan together.
Most of the time Shakugan appears fully human, but she can transform her limbs into massive rock pillars whenever she needs to. It's one of her defining abilities.
She grew up as a poor country girl, living a hard life with her family until her latent powers were discovered. Her parents ended up selling her to a monastery in exchange, which marked a major turning point in her life.
Content compiled by AnimeList.moe from publicly available sources.
