Mermaids are aquatic creatures with the upper body of female humanoids and the tails of a scaled fish below the waist. Pectoral fins adorn their tails, just below where their skin becomes scales. They vary wildly in colouring and are very beautiful. Coral-like antlers, horns or fins protrude from their heads.
They are quite skilled with polearms such as tridents, spears, and halberds. Some trained as warriors since childhood. Mermaids are close and if one is hurt, others will come to her aid. They are capable of gaining sea creatures as allies and use octopi and krakens in battle. Many if not all mermaids are very skilled swimmers. Some have even saved the lives of humans lost at sea, perhaps out of pity or mercy. Mermaids can also move on land despite their tails.
Occasionally there are some who can manipulate the element of water, creating tsunamis and fierce blizzards. Mermaids are capable of infusing objects with great power. When a bully named Merrick attempted to steal Eleanor Olato's pearl necklace, which once belonged to a mermaid, the necklace's magic defended Eleanor and killed Merrick.
It is widely believed that eating a mermaid will grant immortality, but from where this rumor came is unknown. Mermaids live for hundreds of years. They experience time differently to humans and to them, the life of a human is very quick like a flower's. While they will eventually die, mermaids do not grow old and weak like humans. They seem to grow bigger, grander and even more beautiful as time goes on.
- Porkyus - Governor of the Kastolatian Sea and leader of the mermaids of the Sacred Xytegenian Empire. Fell in combat against the Xenobian Rebellion.
- Chloeri - Leader of the Ovis Mermaids. Passed on after the defeat of Shaher.
- Berevra - Sister of Chloeri. Fell in love with Lucius Batraal and gave him the Longicolnis, then took it back after his death. She also rescued the infant Eleanor Olato and watched over her for ten years. Passed on after the defeat of Shaher.
- Aerial - Soldier of the Ovis Mermaids. Became leader of her clan after Chloeri's passing.