Alone among the four emblems, Xuanwu became a deity with a biography, a cult and temples of his own.
Under the Song the name was altered to Zhenwu, the Perfected Warrior, to avoid a character reserved by imperial taboo, and the figure was actively promoted by the dynasty. A hagiography developed: a prince who renounced his inheritance, cultivated the way for decades on a mountain in Hubei, and attained perfection, and who is depicted barefoot with loose hair, a sword, and a tortoise and snake beneath his feet, the emblem he came from now serving as the ground he stands on.
The mountain is Wudang, and the imperial investment in it was enormous. The Yongle emperor of the Ming, who had taken the throne from his nephew and needed divine sanction for it, credited his success to Zhenwu and financed a building programme across the range in the early fifteenth century, employing a workforce reported in the hundreds of thousands and producing palaces, halls and the bronze summit temple. Wudang became one of the great centres of Daoist practice, and the martial traditions associated with the mountain took the god as their patron.
Zhenwu also holds a standing place in Daoist ritual as the subduer of demons, invoked in exorcism, and his image is common in temples across southern China, Taiwan and the diaspora, where he is often known by other titles.
So the same name does two jobs. It is a quarter of the sky in the classical astronomical scheme, and it is a god with a cult, an origin story and a mountain, and the two meanings have run in parallel for a thousand years.