Mélusine

In the best‑known medieval literary version (Jean d'Arras, 1393) Mélusine is the daughter of Pressine (Pressyne) and is subject to a family curse that causes her to assume a two‑tailed serpentine form from the waist down on a recurring day (Saturday in Jean d'Arras). She appears as a supernatural woman who can enter into marriage with a mortal (Raymondin in the tale) on the condition that her husband never see her on that day; she aids in providing wealth and organizing the building of marvelous castles. Variants and regional traditions connect a related figure (Mère Lusine) with fairy builders and the founding of local edifices. Genealogical legends tie her as ancestress to houses such as Lusignan, Plantagenet, Limburg‑Luxembourg and Anjou in medieval popular lore; these attributions function as folkloric origin myths rather than historical genealogy.

Mélusine is usually depicted as a woman who is human above the waist and a serpent or fish from the waist down; medieval and later illustrations and texts sometimes show two tails or wings. In Jean d'Arras she is revealed 'in half‑serpent form' while bathing when the marital taboo is broken, and when enraged or driven off she may assume a more fearsome draconic form. Iconography and descriptions vary by version and region.

She alternates between human and serpentine/fish forms (and in Jean d'Arras may become draconic when her secret is revealed). Narratives attribute to her the capacity to marry a human, bear numerous children (Jean d'Arras records up to ten sons), confer wealth, land, and the organization or supervision of marvelous castle construction, and act as a territorial genius loci tied to springs, wells, forests, and particular castles. She also performs recurring supernatural interventions after departure—lamenting in monstrous form at the deaths of descendants and returning at night in some tales to nurse infants. The tale world includes curses, imprisonments, and magical objects (e.g., the two rings Mélusine gives Raymondin on departure).