Neptral Tower
Neptral Tower is a recurring dungeon located in Gamindustri. It is a tower filled with various enemies and hidden treasure. It first made its appearance in Hyperdimension Neptunia Re;Birth2 SISTERS GENERATION.
Due to the Hyperdimension Neptunia series being one that revolves around the concept of different dimensions and universes, there are multiple Neptral Towers throughout the series, all retaining more or less the same aforementioned purpose and nature.
Etymology
The name is a reference to Spectral Tower, an RPG developed by Idea Factory.