User blog comment:Lifebleedin/how does killua know zenos ability/@comment-24287488-20140123063005/@comment-14902757-20140128070032

Actually, conjurer abilities can be seen by normal humans. That's how the auction held by the Phantom Troupe was possible. Emission is a different story though, the same with transmuters. An aura emitted or transmuted like Hisoka's bungee gum, Zeno's dragon dive/lance and Pokkle's arrows are not visible to normal humans. And actually even to nen users who are not used in gyo.