Marsilikos is an ancient city founded by the Hellenes long before Terre d'Ange's existance. Eisheth fell in love with the city and it became the center to her province, Eisande. The port is only outdone in Terre D'Ange by the City of Elua in both size and prominence. Due to the focus of the D'Angeline fleet to it's southern coastline, the Royal Admiral bases his fleet from there. All of this has led to the title to become one of the most prominent in Terre D'Ange.
The ruler of Marsilikos is always a woman, the first being the angel Eisheth. The title is an extremely rare example of female preference primogeniture. Should the Lady have no daughters her eldest son would succeed her and his wife would gain the title. Phèdre nó Delaunay de Montrève notes that there have been several points in D'Angeline history where men have tried to circumvent this tradition but all have failed.
The Lady of Marsilikos is not tied to any one house or other title. While the ruler of the city may rule over all of Eisande it may not always be so. Throughout the series all of the Ladies of Marsilikos were members of House Mereliot.