Katar
From Revival Ragnarok Online
Definition
Katars are weapons can only be equipped by the Assassin class. Katars are always two-handed so you cannot wear a shield if you are using one. Sonic Blow and Grimtooth can only be used with Katars. The Critical rate is doubled with katar-type weapons. In spite of the fact that a katar wielding assassin has a blade in each hand, it counts as a single two-handed weapon rather than tow dual-wielded weapons, so Righthand Mastery and Lefthand Mastery have no effect on them.