The Cosmic Sea is a vast ocean, in which countless worlds, such as Tarn, drift aimlessly. The Sea is inhabited by the Cosmic Beasts, which are colossal in size. Some have grown large enough to swallow entire worlds.
Most of what is known about the Cosmic Sea comes from manuscripts left behind in the ruins of Old Terethia, and this knowledge has been largely kept as esoteric knowledge by erudite mages and scholars. Because the Firmament is opaque, the Cosmic Sea cannot be observed from within Tarn.
It is not known if there is a Divine Order which presides over the Cosmic Sea.