Therianthropy

In folklore, a mermaid is an aquatic creature with the head and upper body of a female human and the tail of a fish. Mermaids appear in the folklore of many cultures worldwide, including Europe, Latin America, Asia, and Africa.

In Greek mythology, Nereus ( ; ) was the eldest son of Pontus (the Sea) and Gaia (the Earth), with Pontus himself being a son of Gaia. Nereus and Doris became the parents of 50 daughters (the Nereids) and a son (Nerites), with whom Nereus lived in the Aegean Sea.

thumb|An illustration of Grendel by J. R. Skelton from the 1908 Stories of Beowulf. Grendel is described as "very terrible to look upon."

A merman (: mermen; also merlad or merboy in youth), the male counterpart of the mythical female mermaid, is a legendary creature which is human from the waist up and fish-like from the waist down, but may assume normal human shape. Sometimes mermen are described as hideous and other times as handsome.

psychopathological symptom

first millennium BCE High King of Ireland and mythic ancestor of the Laigin

In the Inuit religion, an ijiraq ( or ) is a shapeshifting creature said to kidnap children, hide them away and abandon them. The inuksuk (or inukshuk) of stone allow these children to find their way back if they can convince the ijiraq to let them go.