The Calscroix River rises in the southern Shudderwood, in the county of Lozeri in Ustalav. Initially making a large 'U'-shaped turn to run in a north-easterly direction, the river flows for about thirty-five miles until it is met by its tributary, the Mothburn. The river's 'U'-turn passes Ascanor Lodge on its northern banks. The Calscroix then turns north to join the Buestral River at their confluence twenty-five miles further downstream. The combined river then runs practically due north for a further ten miles or so before it joins the major Moutray River at the northern border of Lozeri. The Calscroix's seventy miles' total length is completely within the Shudderwood.