Undine

Undines are water elementals and a subvariety of Fae. They are embedded within water.

Physiology & Behaviour
Undines are a female-only subvariety of elemental that, like most Fae, resemble humans. Occasionally, one may be capable of identifying fin-like ears on some individuals. Undine skin tones tend to be pale, occasionally reaching bluer hues.

Undines are naturally gifted with water magic. In large hordes, they can create natural disasters such as floods and tsunamis. They can dissipate into water as well.

While it is not proven, some human scholars believe that their bodies are at least 90% water.

Undine hues tend to lean towards the blue palette, much like clear water.

Breeding
Undines will regenerate any loss of hymen after sex. However, this will not apply when mating with humans. In fact, humans are the only species capable of breeding with Undines.

They will mate in a similiar way to humans.

After mating with a human, they will inflict the Undine's Curse upon said human. Should the human be unfaithful to the Undine and leave her, the human will start to acquire accumulative breathing disorders that will eventually lead to their demise.

Undines will gradually become human over the course of a year after mating with one.

Offspring between an Undine and human will always be a human with certain water-related traits, such as the requirement of water at a more frequent rate than humans. However, recessive genes may cause future generations to birth an Elemental Larva. Occasionally, instead of a water-related trait, a certain trait present in Fae in general, such as the inability to lie, may be displayed.

Weaknesses
Undines will get sick in polluted waters. They will also get sick if left out of an aquatic environment for an extensive period of time, unless said environment has the magic of the Fae Forest.

Notable Undines

 * Undyne the Undying (Undertale & Deltarune)

Trivia

 * Undines are the only known Fae to be capable of turning human as part of its natural life cycle.