The Demon Tower is a Pureblood Heartless that appears in Kingdom Hearts 0.2 Birth by Sleep -A fragmentary passage- and Kingdom Hearts III. It is a gathering of Shadows that take on the formation of a large twisting spire.
Kingdom Hearts 0.2 Birth by Sleep -A fragmentary passage-
Aqua first encounters a Demon Tower after finding the five gears in the Castle of Dreams remnants of the Realm of Darkness, and defeats it in battle. She later encounters another one after being reunited with Mickey in the Depths of Darkness, and the two are able to defeat it together.