Inspiration for Tower Dungeon (Slight circlejerk)

Nihei is currently playing a D&D mega dungeon campaign, so he is retelling each session but instead of having the dungeon go down, he made it into a tower going up, that is why it's seems so rushed in its art-style, he has to wait for his monthly session before organizing notes and redrawing anything. Also he is a player, not the Dungeon Master, so he has 0 knowledge of what's going in the background plot