The Underground was once a railway used for travel and gem collection within dark passages and stations. But life is anything but safe in the Underground. It is a dark and dangerous place. Bandits, the Lunar Republic, the Solar Empire, and countless of others strive for power within it.

With the world above still too dangerous to survive in, ponies and others must live life in the darkness and survive. As ponies always do.

Note: I will add tags when/if a new character from the show is introduced.