Undine

The undine is an female elemental water spirit, often found near ponds and waterfalls in forests. They resemble humans, but are themselves without souls. Should an undine marry a human, she will become immortal, but terrible luck is said to befall the husband.

Source
Undines originate from the alchemist Paracelsus' writings around 1530 AD.

Media
Undines appear in the following media:

Novels

 * Berserk