Tiamat’s exact functions as a goddess are difficult to establish. As her name indicates (see below), she was a deification of the primordial sea. Our best source of information for Tiamat is the myth Enūma Eliš , and in fact, there are only a handful of references to her outside of it. Enūma Eliš begins with a description of the two primeval seas, the salt sea Tiamat and the sweet sea Abzu , mingling their waters together to create the gods. In the following battle between Abzu and Ea, Tiamat attempts to appease Abzu and stop the conflict. But when she is later pressured by the lower gods to revenge him, she herself becomes the main antagonist of the story, creating an army of monsters led by her new consort, Qingu. She is ultimately defeated by Marduk, who incapacitates her with his “Evil Wind” and then kills her with an arrow. Marduk splits her in two, creating heaven and earth from her body, the Tigris and Euphrates from her eyes, mist from her spittle, mountains from her breasts and so on. Throughout the epic, there are differing descriptions of Tiamat: she appears both as a body of water, as a human figure, and as having a tail (Tablet V, line 59). These varying descriptions are ultimately reconciled as Marduk turns her limbs into geographical features.

http://oracc.museum.upenn.edu/amgg/listofdeities/tiamat/index.html

Elementally speaking, as the source of primal chaos, it would be a lot easier if Tiamat represented fire, and Abzu represented water, but so be it. Fire plus ocean gives you salt, and Air. Air and Soil give you water, and Air and Soil and Water give you life.

In game context, I reckon that Tiamat was the primal ocean, Tiamat was the world serpent, and Tiamat is the elemental salt that still flows in the blood of the cold blooded that gives them life. And the blood of the chaos born is to some proportion that of the salt sea and the sweet sea.