Stains Upon the Green thrusts the characters into the Tar Kiln, where the ruins of an old dwarven ring fort offers them refuge from the wilderness and its many dangers. Beyond the parapet's walls and the ruined barbican that breaches them stands a keep, built on these borderlands long ago. Abandoned now to the wilderness, its secrets are ripe for the taking. But, within it lies a secret portal that others wish to use to bridge the gap between worlds!