The White Tower

Twilit forms materialized on the shimmering horizon.  A pearlescent tower crowned a craggy island, swathed in mist.  The strange rock formations seemed not quite natural as if made by hands only passingly familiar with real islands.  Enormous corrals, long dead, clustered along the bottom, suggesting a fluctuating water level.  
The only movement on the island was the wavering foliage of cypress trees in the salty breeze.  It seemed more than abandoned, it looked forgotten, forbidden.  
A faint sound echoed over the waves.  A soft, haunting song.

There are many tales in Balonnor about the tower that appears in the mists of the great lake. Fishermen and merchants who sail those waters each have at least one story of how they glimpsed a pale spire rising from the fog only for it to disappear as soon as they approach it.
It is said that this tower is the home of Sidhe. Some claim that if you can make it to the tower, the Sidhe will grant your wish. Others insist that the Sidhe will claim your mortal life and erase your very existence from the memories of all you love. These arguments are mostly pointless, however, as no one has ever managed to reach the tower. Stories exist, insisting that a friend of a friend had an uncle who managed it but no first-hand accounts have ever been heard.

Mistress of Secrets

Many people believe that, rather than Sidhe, the tower is the home of the goddess of secrets. What better explanation for a mysterious tower that cannot be reached than Gwyfyn herself resides there. This version of the mythology of the tower has led many would-be acolytes of the goddess to attempt the impossible.
Those seeking knowledge have spent years or even decades exhausting every fable, account, and fish tale about the tower in an attempt to find that one piece of information that will allow them to reach their goal. Many have gone out on the lake, never to be seen again. Optimistic folks say those acolytes did reach the tower but others recount the number of shipwrecks instead.