Sirens, also called Fishwives, are an odd type of Werecreature, since they look and act like the classical Sirens, who were believed to be a myth in most in Lyssia. They sing beautiful songs that attract their prey, then they dragged it to the sea and then tear it to pieces. They look like hideous mermaid-like beings, with green-scaled skin, webbed fingers, fish-like faces and needle-sharp teeth. Their songs don't affect women and children, only grown men, although its also useless against another Sealord (according to Vega, as it is not confirmed).
While their origin isn't clear, Vega theorize they are therians that used to be the wives of Fishlords, however, they turned their backs on their human sides (like the serpent, Vala).