In the chapter of kamiumi (bearing gods between Izanagi and Izanami) in Kojiki, when Izanagi cut off the head of Kagutsuchi, the god of fire, who was the cause of his wife Izanami's death with his Totsuka no tsurugi sword, they metamorphosed into gods when the blood on the sword stuck to the rock, and Iwatsutsunoo metamorphosed next.
古事記の神産みの段でイザナギが十束剣で、妻のイザナミの死因となった火神カグツチの首を斬ったとき、剣の先についた血が岩について化生した神で、その次にイワツツノオ（磐筒男神）が化生している。