Acquois is the Keeper of Water and thus the Keeper most worshipped by the Water Tribe. He is said to reside in the Lake of Acquois, but has not made a formal appearance in the books as of yet.
When Umbrath turned against Lumeon a thousand years ago, Acquois combined his magic with that of the other Keepers to lock Umbrath away in a deep sea prison south of Xiro. After that, the four Keepers each created one tribe; Acquois's being the Water Tribe. Since then, he is in charge of this tribe's vocation ceremony.