Tiamat is the primordial mother-goddess of Babylonian myth. She bore all the creatures of the world and many younger gods with her consort Apsu, the god of fresh water. She is the "shining embodiment" of salt water and accurate to Kazuma Kaneko's designs for her in the Shin Megami Tensei series, a large portion of her body is described as consisting of "lower parts" (I.E., genitalia). She defended her children from Apsu who attempted to kill them all with a great flood (in the Enuma Ellis) but later fell in to conflict with them when Marduk opposed her choice of Kingu to be the leader of her Godly children. Marduk slays Kingu and uses his blood to create mankind. Although she bore many monsters to battle Marduk, he overcame them all and eventually slew her.
A creature named Tiamat also appears in the Final Fantasy series, but is based on a Dungeon & Dragons monster rather than this Tiamat of Babylonian myth.