This story is Light-dark in that there are only dark tones in the story. It is not grimdark.
Milk Spot and Verdure Patch are both unicorns that live on Secantor Island: A place with advanced steam technology where many a pony, griffin, and minotaur live. The island is completely covered in buildings that rise higher and higher, but not much goes well for those living lower and lower.
It might be impossible, and the tensions between Secantor Island and Equestria might end up sparking a war, but two unicorns will have to work together to escape this place and see if 'Equestria' is real or just a legend created by those who watch over everything in this dark world.
This is a collab between David Silver and I.