Aspect Of Serration question

Hey Folks, i have question… im playing 3 weeks in a row… so much time as necro but i havent seen this aspect even ONCE… i want to make bone build but… without it its weak…
i have all items to that build except that one. and there is a question…
Do i need to use passive ability with ossified essence to drop that aspect ? cause im using Summoner necro at this moment…