The Opalin River is a major river found running through the Emerald Forest in the northwestern regions of Tersodia. Its source is found in Skyfract Minor near Talonforge, flowing eastward before turning south and then westward to flow into the Gulf of Mana. The Emerald Lake is found midway along the river.
The Opalin River is known for its clear, pure appearance that attracted settlers to establish cities such as Emeraldshore. While not navigable by boat, the river and connected lake hold enough fish to sustain local populations. The river also makes the surrounding soil perfect for orchards and vineyards, leading to many being located in the surrounding forest.