The effect of a good Nocturne gank can be devastating. He's especially useful in the way he can help control mid lane. Sometimes, Nocturne's mere presence can prevent an opponent mid laner from stepping forward. That opens up even more room for him and his team to take over the map and the tempo of the game.

Why is Nocturne so good right now?

Early-game power and roams make Nocturne strong

Nocturne and the current meta fit very well together, which makes up for one of the big reasons why he is performing so well. Previously, Nocturne was only considered a jungler but now the assassin is just as strong as a solo laner.

Is Nocturne good early?

Strength in early game/laning – low/medium

In the early game, Nocturne is a pretty linear champion in terms of what he can do: hit you with his Q, fear you, and run you down with autos. That's not to say that you can't do anything as Nocturne early but you definitely have difficulties finding ganks and fights.