Who is Apsu from Myths from Mesopotamia: Creation, the Flood, Gilgamesh, and Others and what is their importance?

Apsu is the father of the primeval gods. She is also the wife of Tiamat. Unhappy with their noise, Apsu decides to murder the gods, only to be slaughtered by his own grandson, Ea. Ea's act leads to a war between Tiamat and the younger gods, in which Tiamat is slaughtered and used to create the Earth.