There are few of them, and few have fully understood them until now. The wondrous watch towers. Hardly anyone knows where they came from or who created them, but they are one of the most powerful objects on all planes. Without the specific conjuration word, they are only small figures. They will take you to fortresses that allow you to travel between the planes.
But not everyone can simply own a tower, the tower looks for its guardian and binds itself to the soul of its owner. If this bond lasts long enough, the interior of the tower will be shaped according to the needs of its owner.

Notes: You have to form a special bound with the tower.