This newfound power didn't just change her magic; it physically altered her appearance, giving her the iconic "three legs":
Her left leg, which looks like a more traditional bird-like claw. Reiuji Utsuho
Her right leg, encased in a metallic "Elephant Foot" looking device. This newfound power didn't just change her magic;
Before her brush with divinity, Utsuho was one of Satori Komeiji’s loyal pets, living in the Palace of the Earth Spirits . Her world changed when she was told (likely by Kanako Yasaka) that she could swallow the divine spirit , the three-legged sun crow. By doing so, she gained the ability to manipulate nuclear fusion , a power far beyond the typical scope of Gensokyo’s residents. it physically altered her appearance