If they continue onwards, they will end up at the western edge of the forest and the barrier that stops them from entering the Darkness. They will be able to see the water turn into a black sludge there and the land there is eerie black and cracked. In the distance there are some buildings, but everything about the Darkness seems dead and just in "ruins".

If they throw anything out of the barrier (items do go through) they will either vanish into smoke in the air or are consumed by the black sludge in the ground. Alternatively, they can also turn into sentient darkness monsters that will start running away from the Barrier and into the wastelands.