User blog comment:Dj0z/Dj0z's Assassin Nocturne Guide/@comment-5031932-20120526065109/@comment-5045559-20120526183129

Go straight to the "Teamfights" part in the "Tactics" section for your answer.

FM is good, no doubt, but also very costly (warmog's is cheaper) and providing only 20 AD and slow for offensive stats. For this Nocturne it is a luxury item, or a situational defensive item when you fail to stay alive because you already have great speed passively, and get 2 MS steroids (Q and Youmuu), and already have a spammable CC, unlike, say, Wukong. Unlike the typical nocturne, you can use those very often because thise build gives ~34% CDR endgame, that's 2 Q+E comboes in 8 seconds.

That's why i'd go mallet only if i'm getting assassinated, like by a fed twitch or something, because regarding teamfights, you need to be extra careful.

Oh yeah unless you rush the Phage/Mallet, which delays your damage output by quite a bit, you're still better off with the reliable CC of E imho.