The dark swamp is different from a normal swamp. It's covered with fog. You can hardly see anything because of that fog. Poisonous berries grow in this swamp. They look like sweet berries but they are poisonous green. You can pick them. If you eat them you will be poisoned. There is also a giant water snake in this swamp. If you throw meat or fish in the water you can lure it. When you've done that you have to fight with the beast because the water snake will attack you. I don't know what it would drop. Maybe a snake's tooth with which you can brew a potion. The dark swamp is very rare.