True antagonist of the Seventh Singularity referred by other gods and Kingu as they "Mother".
One of the Primordial Deities in Mesopotamian/Sumerian Mythology. Tiamat is an Earth Mother Goddess. Along with Abzu, she was manifested of the Sea of Dawn - an Ocean of Void that lies below the Underworld of Ereshkigal, said to have once been under the administration of the god Enki.
In Sumerian Mythology, the gods were given birth from the pairing of Tiamat, who is the salt water, and Abzu, who is the fresh water. Afterwards, the gods, whom are their children, waved their banner of revolution against the primeval father Abzu and acquired supremacy over the world. At this moment, Tiamat gently approved the deeds of her children. However, the gods pointed their blades even at Tiamat, their mother. Tiamat, in her grief and disorder, gave birth to 11 Magical Beasts as her new children, and they altogether had a showdown with the gods. At the end of the conflict, Tiamat and her 11 Magical Beasts were torn apart. It is said that the gods tore up her corpse into two, forming heaven and earth from it.
As of obtaining the Holy Grail that Goetia stored within the heart of Kingu, the Primordial Sea initially manifests a human-scale corpus known as Femme Fatale -- roughly 160cm in height, clad with arm and leg restraints. Gilgamesh refers to this as Tiamat's Cerebral Corpus; it is suggested to represent whatever remains of Tiamat's mind or consciousness.
Following the annihilation of the Cerebral Corpus, the Sea of Life manifests Tiamat in the form of a Titan. However, in the circumstance that Tiamat faces a severe threat, she enacts Self-Modification and Saint Graph Dilation Operations to assume a Sphinx-like Draconic Corpus -- referred to as her "true appearance". After the Draconic Corpus is imposed with the "Concept of Death" by the Old Man of the Mountain, Da Vinci confirms that Tiamat's Saint Graph Core is situated within its brain.
