Mundus Subterraneus is a mediumnic society that aims to produce what we called the Collision: works that obeys to alternate realities, dystopian cartographies, micro-history, experimental anthropology, post-archive research, heteronyms, using a concept invented by Jorge Luis Borges: the hrönir. The hrönir would be those objects that appears in our world but belongs to another, due to its improbability of existence or its physical qualities. These objects would be generated in their original world as a consequence of an intense believe in their existence.