Other Dimensions

Beyond the Overworld, Nether and End, there are tower variants built for dimensions that other mods add:

Each of these is tied to biomes from the mod in question. If that mod is not installed, the biomes do not exist and the tower simply never generates - it costs nothing and causes no errors to have them defined.

The same is true of the waystone that generates on the roof. With Waystones installed each tower gets one, which turns the whole set into a fast-travel network: climb a tower, link its waystone, and it becomes a place you can return to. Without Waystones the towers generate exactly the same, minus that block.