Currently I have a guillotine cross, but a while ago, this skill does not work properly because the required item (Venom Knife) can not be equipped.
Before the "Venom Knife" were equipped as if they were arrows and only with this you could use the skill, but now only I get a message stating that I equipped a bow but neither can and this was never necessary (I could use daggers or katars and skill without problems).
In addition, I have asked other players who have assassins, assassins cross and guillotine cross, but neither works for them.
(not really know if these errors are posted here, but I'm a bit lost ¬ ¬ and sorry if there are inconsistencies in the text, as I am using the translator google.com ._.)