Before the time of the Baali Wars, Mashkan-Shapir was the headquarter for one of the first Baali, Nergal, near the banks of the Tigris, where he was worshipped as the consort of the Underworld goddess Ereshkigal.
It was a place of wondrous advancements for its time -- it boasted two harbors within its battlements, river streets for ships and a temple to Nergal over a quarter of the city in size. Mashkan-shapir served as the center for Mesopotamian Baali for centuries, sheltering the malignant darkness beneath the skirt of its walls. In his vast temple, Nergal conducted corrupt rites, afflicting his mortal followers with plagues and sloughing the flesh off their bones with which to decorate his temple interior. Aided by a loyal revenant line, the D'habi, Nergal discovered the sleeping body of one of the demonic children the Baali and started preaparations to awaken him.
When the news of Nergal's reached his brother Moloch, he made sure that the vampires of the Second City would notice this, ending the charade of the Baali to pretent they were normal vampires. The thirteen Antediluvians waged war against Nergal and his ilk, when they could not breach the doors of his temple due to his demonic magic, Lasombra priests of the goddess Ereshkigal, using powers now lost to the clan, penetrated the temple through the shadows that hovered within and flooded Nergal's haven with liquid darkness. Nergal and his remaining loyal followers were washed away by the black tide and vanished into whatever domain from which the Lasombra summon their servants, and Mashkan-Shapir was forever lost to the bloodline.