Players who climb up the 30' chimney in Klarg's Cave (rope/climb) find a 60' narrow passageway that leads north to the small landing at the lower right corner of this map. Cave room descriptions and encounters are found here: https://www.lightheartadventures.com/side-quests/free-dnd-one-shot/, which has a ladder up to the surface in the last room, rather than a portal, with players finding themselves somewhere in the Neverwinter Wood. I popped a Crystal Golem into the last room (CR13!!) which melds into the walls when the ceiling starts to collapse.