Discovered in Farmstead Infestation and Pest Wrangling: a Farmer's Folly, the Purple Forest is an underground forest accessible through a cave network under a barn in Blackrose Farmstead, southwest of First Landing.
It's a strange forest where plant life has developed a purple pigmentation to survive in the absence of sunlight. Fireflies and flash beetles illuminate the caves. The forest is roughly a mile and a half in diameter. There's a lake with water pouring into it from the walls.
This forest is home to spiders, giant newts, and two aggressive "factions" of animals: Blindheim and Badgers. Both of these groups have defeated a party of Guild adventurers each. The Blindheim in Into the (Purple) Woods, interestingly, did not eat or even kill the fallen adventurers but the Badgers in Into the (Purple) Woods 2: And Home Before Dark killed two adventurers as the rest recalled. The Badgers were led by a particularly dangerous Mutant that was slain by an adventuring party who went down to investigate the casualties in Into the (Purple) Woods 3: No One is Alone.