Heavenly Lord Xin 辛天君 played a very important role in the rise of Thunder Magic 雷法 in the Song-Yuan dynasties. Besides being the celestial commander-in-chief 主將 of the Thunder Magic of Hunyuan 混元道法, Xin was the interpreter of the magic. As one type of the Magic of Summoning Heavenly Lord Xin 辛天君召合法術, the main part of the Thunder Magic of Hunyuan had complicated textual connections with another type of the Magic of Summoning Heavenly Lord Xin and other sorts of Thunder Magic. Such connections reflected a tendency for different forms of Thunder Magic to borrow from and integrate with each other.