"Small and suited for ritual purposes, they are often crafted of materials more simple than metal. Wavy and serrated however, they are better suited for combat than their purpose might imply."— Game Guide(src)
Most of the time, though, Witch Doctors will not use the ornamented knives directly, preferring to channel the power of the Unformed Land through these blades. Most Ceremonial Knives are made from bone, but obsidian, chitin, metal, diamond and stone blades can be often encountered in game.
In addition to normal weapon-specific attributes, all Ceremonial Knives may roll Maximum Mana and Mana regeneration.