I dunno exactly where it is I've been waiting for an update but it's near the place you find the lizardmen tribe where I think it's called the dark swamp
Oh the witch does require the village but she's not found there, you find her by doing some quests for the priestess until she is missing 3 acolytes and needs help. During that quest you find one by exploring the swamp and follow her to there unlocking the dark swamp. (Also you gotta explore not just go there since first encounter and such)