Like a grim eagle upon it's nest, the great black block of Tannia Castle looks down upon the city of the same name. Despite the fact that some of those brought within it's walls never come out again, the castle is still looked upon well by most of the city's inhabitants, a place of protection rather then a place of terror.
If thrown into a moat or a ditch, they react with water to make an area of ground a foot wide and solid enough to walk on rise from the bottom. If eaten-well, the body of the one who ate one of them is a real mess. Used to storm moats and forge rivers, streams and ditches. Must be kept dry until used.