Where the Beathamuir River crosses a water leyline, the Tower of Azül rises from an island in the river's center. The tower is ancient—built of blue-black stone that seems to drink in light—and has served many masters over the millennia. Currently it stands empty, its last occupant having departed (or died) within living memory.
The tower's position on the water leyline makes it valuable to any mage with water attunement. The river itself behaves strangely near the tower: it never freezes regardless of temperature, and fish caught in its waters near the island are said to grant prophetic dreams when eaten. The Neth tribes who range through the Northern Plains consider the tower taboo and will not approach within a mile of it, though they refuse to explain why.
Whoever built the tower understood both hydromancy and architecture that has not been replicated since. The interior is rumored to contain chambers that exist partially underwater, partially in air, with no clear boundary between—rooms where one can breathe liquid and drown in air.