The Bog Hag

From the introduction: An important trade village lies along a river. A few miles away lies the Hagsbog, a forbidding swamp. The villagers generally avoid this maze of vine-choked waterways, algae-covered pools, moss-draped trees, tangled briars, and muddy marshes. Various creatures inhabit the bog, under the thrall of the evil green hag, Mamawaldi.