Yron: According to the Liber de Angelis, a fifteenth-century manual of magick, Yron is one of several demons who serve beneath the infernal king Bilet, also known as Bileth. Bilet and his servants can be conjured up by the magician in order to inflict disease. The demons will target any of the magician's enemies, bringing them fevers, tremors, and weakness in their limbs. The demons will not relent unless they are called away from their evil task by the magician himself.
SOURCE:
The Dictionary of Demons written by Michelle Belanger