From publisher blurb:
Level-3 D&D 5e + Shadowdark Adventure
In The Cursed Cairn, the characters find Verdant Hollow forest flooded and turned into a noxious bog. Even wildlife has been transformed into evil, more aggressive counterparts. Two crones and an elf herbalist approach the characters looking for their help. The old women claim that her sorcerous sister, a part of their broken coven, went into a forlorn tomb and dabbled with otherworldly powers. She brought ruin to the forest.
The characters forge an unlikely alliance with the two hags and the elf, and delve into the befouled depths of Verdant Hollow. They find the bog-forest infested with swamp kappas, and dangerous birds of prey. In the strange fey tomb, the party confronts the greedy hag. She has become more powerful and threatens to destroy the forest. Can the characters stop her? Is their alliance with the witch's sisters a good thing, or something to be concerned about?