The River Grismerie is about 600 miles long and draws waters from the west facing side of the Grey Mountains. At its source, the river flows through the north edge of the Loren Forest, and many Bretonnians regard the river as strangely enchanted. Its course takes it directly through a great lowland bowl, towards the Gisoreux gap, where the river is joined by the Ois and continues westward to the sea. Above the Ois, the Grismerie is navigable by large barges as far as Parravon, but sea-going vessels are restricted to the lower reaches and the wider, deeper Ois tributary. The river is crossable by ferry at Mousillon, but the only bridges on its entire length lie at Parravon and to the east of that city.[1a]
The river itself located between the Grey Mountains and the Massif Orcal, and has cut a great valley. Though the land around the river is fertile, the terrain is mountainous, and marauding bands of fell creatures are not uncommon in the area, so the settlements of men are few. Despite its inhospitable nature, the valley holds great tactical importance, Axe Bite Pass, one of the few gaps in the mountains that can afford access to the Empire, comes into Bretonnia near the valley. Should this area fall into enemy hands, trade and troop movements between the lands of Bretonnia and the Empire would be severely restricted.