Mermaid/Merman: A race of half-human, half-fish creatures that live underwater and rarely come to the surface world. Mer has some control over water. Mortality level 4
Sirens are highborn mer, with powerful voices, and excellent control over water. Mortality level 5
Mer hierarchy goes like this, Royals - Nobles - Commoners
Royals are almost always Sirens
Some Nobles are Sirens and mainly regular mer
Commoners are always regular mer
Mermaid, masculine merman, a fabled marine creature with the head and upper body of a human being and the tail of a fish. Similar divine or semidivine beings appear in ancient mythologies (e.g., the Chaldean sea god Ea, or Oannes). In European folklore, mermaids (sometimes called sirens) and mermen were natural beings who, like fairies, had magical and prophetic powers. They loved music and often sang. Though very long-lived, they were mortal and had no souls.
Though sometimes kindly, mermaids and mermen were usually dangerous to man. Their gifts brought misfortune, and, if offended, the beings caused floods or other disasters. To see one on a voyage was an omen of shipwreck. They sometimes lured mortals to death by drowning, as did the Lorelei of the Rhine, or enticed young people to live with them underwater, as did the mermaid whose image is carved on a bench in the church of Zennor, Cornwall, England.