Towers are expensive and difficult to construct. A lone tower is highly unusual and suspect. Towers are looming and ominous. All of these together help the writ

Towers are expensive and difficult to construct. A lone tower is highly unusual and suspect. Towers are looming and ominous. All of these together help the writer convey that the character within the tower is powerful, odd and scary. They also set up the story of adventuring through the tower, floor by floor, in increasing levels of difficulty —as illustrated in the great fantasy movie: Bruce Lee’s Game of Death. :D