The Watchtower is a fortified defensive structure situated on the northern wall of Yanille. Its primary purpose is to defend the city from the ogres that inhabit the nearby Feldip Hills and Khazard's Army that inhabits the Fight Arena to the north.
The Watchtower was built to defend the city of Yanille, which is situated very close to the Feldip Hills. This has led to numerous attacks, usually by the ogres that inhabit the area and continue to push their way further into southern Kandarin.
The tower is managed by the Watchtower Wizards, who operate the magical generator on the tower's top floor. A number of watchmen also protect the tower from invaders. Also, the guard may tell you that it is private if you try climbing up the main ladder, so, you will need to have an agility level of 18 to enter by the trellis.
The Watchtower is protected by a magical generator, which is fueled by a number of powerful crystals. During the Watchtower quest, the player must recover these crystals, which had been stolen by the ogres.