Considered by many to be a relative of the glimp-shell (although some researchers claim the two are the same species, either as different sexes or at different points in the life cycle), the Plodder-Shell is a similarly implacable pack animal.
Unlike the glimp-shell, Plodder-Shells are not used as mounts, but typically only as beasts of burden. This is well-founded: they are capable of hauling tons of goods, and they walk in one direction. Always.
Even when asleep, they walk forward. Like sharks, if they ever stop moving, they die (the largest specimens, becoming too heavy to move, die shortly thereafter). They also cannot move backward, and so are typically kept on curved tracks so that they may continue to walk.
Plodder-Shells see little use in the Sorrowfell Plains — merchants typically find they move too slowly — although they are occasionally seen in Scandshar.
Plodder-Shells do not engage in combat; instead, they trample anything lacking the sense to get out of the way. They always move in a relatively straight line, never turning more than 45° between squares. As such, if the Plodder-Shell is at the 'X' and is facing toward '2', it can move to 1, 2, or 3.
Assuming it uses its first square of movement to move to '1', it can continue in this fashion. On its next movement, it can move to 9, 10, or 11.
A typical Plodder-Shell costs 1,000 gp, and can push or pull 1 ton of cargo per level. As such, the typical specimen presented here can push or pull 4 tons of cargo without difficulty.