Hey guys I'm just some lowly gold pleb but have been playing Nocturne off and on for almost 2 years he is probably my favorite champions in terms of lore and game play. He offers a variety of play styles and can adapt the enemy team being either a deadly assassin or a front line bruiser the enemy just can't ignore. Either way the enemies back line will hate you for the fact you can dive into them and ignore their cc( in general its only one spell) with your pesky spell shield.

Pros

High Dps
Hard engage
Spell shield
Scariest ult in game

Cons

Will be squishy if you follow the DPS build
can be bursted easily after initial engage
lacks hard disengage

Passive:Umbra Blades
This passive is basically what lets you dive into whole teams and live because this + bork and/or hydra gives you so much sustain. It also make your aa do 120% of your AD as AoE.
It has a 10 seconds cd that is reduced by 1 second for each auto attack you preform, Making you do tons or dmg when you attack after you use your Q

Q: Duskbringer
Your Q is an amazing spell that provides MS and AD buff. At max lvl this will give you a bonus 35% MS on the trail it leaves behind + 55 AD. If it hits an enemy champion the trail it leaves follows behind them providing you with chase. This + your passive are what allow you to do so much burst dmg your other spells mostly supplement them.

W: Shroud of Darkness
A spell shield on a champ like nocturne is amazing it basically allows you to dive into teams without having to worry about their initial hard cc and when timed properly makes it impossible for the enemy to peel for the adc's and mages you dive. The spell also has a passive bonus to AS making your passive reset faster due to more aa's, not to mention the bonus is doubled when the shield is triggered allowing you to do even more DPS.

E: Unspeakable Horror
The ability to fear the enemy is such an underrated cc in league and allows your to win almost every duel with Nocturne, also when the enemy is feared Nocturne gains a huge MS buff when running towards them.

R: Paranoia
This ult is 2Spooky4Me. It severely reduces then enemy's Field of View and makes them **** their pants. It has a scaling range and at lvl 3 allows you to collapse from about the same distance as TF. On top of allowing you to dive champs and lower their vision it also does damage when you land allowing for more burst to your combo.