The son of Kyuss appeared in third edition in Living Greyhawk Journal #1 (September 2000). The spawn of Kyuss appeared in the third edition Monster Manual II (2002). The spawn of Kyuss was detailed in Dragon #336 (October 2005) in "The Ecology of the Spawn of Kyuss".
A son of Kyuss is a walking corpse with worms protruding from its facial orifices, which attempt to burrow into living beings and kill them. The spawn of Kyuss are the footsoldiers of Kyuss, part of the Wormgod's wormspawn legions.