A Shamkniv is an ogre torture device used to torture Mercadirs who fail their assignments. Keefe is threatened with this in Nightfall, and it's used quite harshly on Lady Gisela in Neverseen. King Dimitar wields this weapon. It's jagged so each cut leaves a scar, and if someone seriously disappoints the king he dips it in flesh-eating bacteria. Usually, it's only used for one or two cuts for a first offense, but in Lady Gisela's case, Fintan sentenced her to many. Lady Gisela was cut in places such as her neck, face, and chin. In book 6, Nightfall, it is revealed by Sophie Foster that Alvar Vacker was hurt in several places by a shamkniv.
A dagger-size weapon, short and heavy, made of black metal that curves like a crescent moon. Serrated, but "you won't know until you feel it."