Physical Description: According to Greek mythology, they were creatures that were combinations of women and birds in various ways. Sometimes they were represented as birds with large women's heads, bird feathers, and scaly feet. Sometimes they were female figures with the legs of birds, with or without wings, playing a variety of musical instruments, sparrows from the chests up and women below, or little birds with women's faces. Other civilizations say they were similar to mermaids, human with a fish tail for legs.
Other Name(s): "Winged Maidens"
Origin: Greece
Creation: Daughters of Phorcys, their father, or Achelous with Terpsichore, Melpomene, Calliope, or Sterope
Characteristics: Lured nearby sailors with their enchanting music and singing voices to shipwreck on the rocky coast of their island or lulls them to sleep then climbs aboard to devour them. Only two to five have ever existed and there is great dispute over their names, Thelxiepeia/Thelxiope/Thelxinoe, Molpe, Himerope, Aglaophonos/Aglaope/Aglaopheme, Pisinoe/Peisithoe, Parthenope, Ligeia, Leucosia, Raidne, and Teles are believed to be some of their names.
Defeat/Weakness: Cursed to remain birdlike until a sailor can sail by without falling under their spell, losing a singing contest with the muses and losing their feathers, Orpheus playing his lyre, or death if someone hears their song and escapes
Physical Description: Creature with the head and forequarters of a horse and the tail and hindquarters of a giant fish
Other Name(s): "Hippocamp"
Origin: Greece
Creation: Poseidon created them
Characteristics: Both freshwater and saltwater living. Sometimes have wings depending on the species.
Defeat/Weakness: Never used in battle, but used for transportation by Poseidon
Physical Description: Creature like a giant serpent living in the ocean with sharp black scales and flaming red eyes
Other Name(s): "Sea Dragon"
Origin: Greece
Creation: Created by God
Characteristics: It was known for attacking vessels and grabbing and swallowing people
Defeat/Weakness: Can be killed by renowned fishermen, usually with a spear
Physical Description: Creature like the giant squid with spikes on its suckers
Other Name(s): "Crab-fish"
Origin: Greenland
Creation: Here since the dawn of time
Characteristics: Cannot reproduce. Said to inhabit the seas of Norway. So large, it leaves a whirlpool in its wake. Spends three months eating or hunting and three more digesting.
Defeat/Weakness: None
Physical Description: Creatures that live as seals in the sea but shed their skin to become human on land
Other Name(s): "Silkies" / "Sylkies" / "Selchies"
Origin: Scotland
Creation: No definitive origin, have always existed
Characteristics: Appear as seals in the sea, sometimes luring fishermen to their death, and human on land, sometimes being forced into a loveless marriage, then later returning to the ocean
Method of Identification: On land, finding their seal skin will reveal who is a selkie because they will want it back
Defeat/Weakness: Can be forced to stay on land if someone steals their seal skin and have to marry whoever found the skin