While currently not found in the game, various texts, both outside the game and inside of it, speak about it.
It's a tower built by the Ancients and is heavily linked with the power of the Black Stones and various incidents connected to it.
Back in the time of the Ancients it's said that a "Tower of Will incident" happened. In recent times another "Tower of Will incident" seems to have happened, albeit the details are scarce.
An excerpt of the 23 Books from an Ancient Codex says:
A soaring tower lies at the heart of the Black Desert. Fix together the symbol-engraved Black Stone shards and imbue the tower with cleansing light. When this light swells from the tower and spills into the Black Desert, the two sides of the world shall open.
- While currently not found in the game, the old Korean cinematic for the game featured it, speaking of the recent Tower of Will incident that is still spoken of in the Korean timeline of events. You can check the old cinematic here