The underground part of the Church was hardly smaller than the surface section, apart from the boiler that symbolized the Divine Power of the God of All Mechanisms, the Church's underground area served many purposes.
In this world, the two churches were not hindrances to progress but were pioneers leading the Goblin Race on the path of evolution. Besides preaching, the priests of both churches were also researchers of the wisdom of the God of All Mechanisms.
In terms of this world, these priests were Mechanical Scholars, surpassing even Mechanics.
Therefore, mostly, the underground part of the Church of the God of All Mechanisms was filled with research labs dedicated to the priests.
Bright gas lamps illuminated the entire laboratory, making it clear and unlike some stereotypes, this type of laboratory involved in human research and flesh transformation was not a dark, evil place.
On the contrary, places requiring delicate surgery needed to be exceedingly bright.