Encompassing the whole Mediterranean sea and centered around Castel d'Ombro on Sicily where the Antediluvian was rumored to rest during his time in torpor, the Sea of Shadows was among the more prominent and powerful fiefdoms, vastly profiting from the fall of Constantinople, as the Lasombra were able to annex most of the Byzantine holdings.
Although [Lasombra] was the nominal ruler, his childe Montano was responsible for running the fiefdom while his sire contemplated the great darkness of the Abyss. The Sea of Shadows itself became politically divided during the Shadow Reconquista, as both sides of the clan (Muslim and Christian alike) claimed the blessing of the Antediluvian for themselves.
With many Lasombra princes in the Levant and Italy only telling their sires in the Sea of Shadows what they wanted to hear, the organization ultimately collapsed during the Anarch Revolt. The Clan Founder was thought to be destroyed and Montano defied his clan to become the first Lasombra antitribu.