Commonly refered to in Dr.Torburn's Classical Mythology class; they are Nymphs who often sex men to the point of death, or often jumping men's bones in their sleep!
"On the Island of Lemnos, Hyllas, a member of the Argonauts was getting water, when all of a sudden Three NYMPHO NYMPHS slowly emerged from the water. Alas, poor Hyllas was never seen again...he got sexed to death!"
by tbaylor June 12, 2008