Mossy Flats of Carivan

Carivan (Ravnica) is a massive city-nation. In the Golgari region, Mossy Flats was a region in the swamps that was worked by farmers that specialized in cultivating a specific sort of moss that grows in the bogs - one great for healing potions. Recently, they've instead been farming potatoes in the bog... special potatoes. Taters infused with some unseen, ethereal worms of another eldritch world where plant-like species dominate. Citizens are secretly sacrificing specific youths over several months to complete a doorway to draw "He of a Thousand Eyes" - the potato monster from another world.

Really, do whatever you want with this small town. That's just what I used it for in my homebrew game. The team found the Plantinomicon sort of book that can summon boss fights that grow in difficulty and reward incredible plant-based magical relics.