“ Creates a river source in a 3x3 section of flat land. When you create many rivers, it may appear in the Cube. ”
River Source is an item that creates a single tile of freshwater, which can then be expanded by lowering adjacent terrain. It must be placed on terrain at least 1T high and 3x3 wide. River tiles are required as habitat for freshwater organisms and spread moisture like ocean. It first appears in Episode 1 of Story Mode.
It is the only item required for gameplay which will not appear in Free Mode without loading items from a Story Mode game or a Free Mode game which has previously acquired it from Story Mode. Only one is required and may be expanded indefinitely. Spreading river tiles will spawn further River Sources. Though river can be connected from higher to lower levels, creating waterfalls, ponds and lakes can only be the same depth throughout. Attempting to deepen them will simply create a hole which freshwater tiles flow into.