Evening summoners!
This would be my first build I make, wont be the last if I get good credit for it.

I changed Nocturne recently to my main from Akali. In my point of view, Nocturne and akali is much alike in ganking and chasing but what made me change to Nocturne is his better jungle/farming ability.

Your job as an assassin is to go in, kill and then get out!

Hear me out!

Pros:
+ Great early game ganker
+ Insane farmer
+ Good chasing ability
+ All of his ability works both ways, chasing and running
+ Good jungler, almost at Warwicks level.
+ Sick ultimate ability
+ And a little side point, great voice

Cons:
- Squishy early game
- Target to CC cuz of high damage
- Vulnerable to CC (Not so much when Shroud of Darkness can be used)
- Enemy team will flame when you use ultimate :) But thats a good thing isnt it?

Umbra Blades (PASSIVE)
Great passive, this will let you stay on your lane alot longer since with Doran's Shield you wont get any health potions. Makes it easier to jungle with this, almost puts you in Warwicks level in the jungle :) Faster AS, faster recharge on the passive.

Duskbringer
Great harassment, chasing and flee'ing ability. Cast at your enemy and it will often hit since it travels fast. When it hits, it leaves a trail behind them when they run from you, they WILL run from you, and when you chase them on this trail, you move faster, hit harder and you move thru minions and other champions whom stand in your way.

Shroud of Darkness
First ability you will play full skill in. Great passive, increase your AS (This will help alot for your Umbra Blades) and Active is even better! If you block a spell, can be anything from aoe to single target ability, you will gain dubble, you heard me, dubble attack speed then its passive use for 5 seconds! This is alot of attack speed and alot of damage you can burst out with, specialy if you have duskbringer on them.

Unspeakable Horror
Hmm, what to say about this one? The name says pretty much what it does. Horror! When you cast this on your enemy, it will deal low about of damage, but if you stay in 500 range of your target, after 2 seconds, they will become feared! This is great to interupt such ultimates like katarina, warwick, karthus and others.

Paranoia
The worst ultimate in the game! For your enemy that is. This is so cool, finaly a champion with a ultimate that will get your enemy to flame more then to Karthus Requiem ultimate!
This is great use when your enemys run, and your ghost/duskbringer is on cooldown and you cannot chase them down. Activate, target, kill and win! Your enemy wont know what hit them!

Ghost is a must for Nocturne. It works great with Duskbringer, either for your escape or your kill. But if you like Flash, use it, it might be helpful too. But I wont recommend you to use Flash cuz of its long Cooldown.
For second I take Ignite. You can use Exhaust aswell or Smite if you want to jungle (then you have to change Archmage's Savvy to Plentiful Bounty or to Cripple depending if you wanna jungle or use Exhaust).

Other great Summoner Spells you can use:
Clairvoyance - Can be used with your ult to show enemy jungler and jump on him or someone who escaped gank.
Teleport - Can be useful to gank, by teleporting on a ward in brush or a minion (Maybe even a Noxious Trap if you play with Teemo).

What you should never take:
Heal - You will get enough heal from Bloodthirster and Umbra Blades.
Clarity - No, you benefit more from the golem's blue buff.
Rally - Why does this even exist?
Fortify - No chance, let tanks and supports use this.
Revive - Totally useless. You wont die so easy!

Masteries I took a standard 21/0/9 build with improved Ghost and Greedy in Utility tree.

Easy rune build
Greater Mark of Desolation x9 standard rune for most dps champion.
Greater Seal of Alacrity x9 this will help you early game with Umbra Blades. If you donot want this, you can use Greater Seal of Fortitude or Greater Seal of Focus to ease the cooldown on your abilities.
Greater Glyph of Malice x9 You will alrdy get crit from your items, but since Infinity Edge isnt included in this build, you can use extra crit chance.
Greater Quintessence of Malice or Greater Quintessence of Desolation x9 But I prefer Malice for its good crit chance early game. End game you will have about 60% crit chance.

Now for the items!

First of you start with a Doran's Shield, probly know why. Can stay lane longer with its 120 health and 8 hp5 and less damage since it gives armor.

Early game level 1-10
You should keep your dorans until late game, its still good even at lvl 18.
So first item you should buy when you first recall is The Brutalizer, this item is good for its Cooldown reduction, AD and armor penetration! If you have some gold spare after this item you get your Boots of Speed.
After The Brutalizer and Boots of Speed you need to buy Zeal. Give you extra movement, AS and crit. When you made your Zeal you build up Berserker's Greaves. This has to be done before timer hits 20 since you wont have much chance to creep kill.

Mid game lvl 11-16
Now the damage begins to pour out from you and other champions. So now would be a good idea to get Vampiric Scepter for some extra life stealing. After thats bought, you start building The Black Cleaver and after that you finish The Bloodthirster. This should be before you hit level 16. If you like, start building Phantom Dancer.

Late game lvl 17-18 Now you should have gotten some kills and assist. So gold shouldnt be a problem. Now build Phantom dancer if you havent already, if you got it start building Guardian Angel. Start at Null-Magic Mantle if theres alot of AP and if theres alot of AD you start buying Chain Vest. After you done with your Guardian Angel, ofcourse sell Doran's Shield to make room for it. you got to make Youmuu's Ghostblade. You have alot of AS already, so this will help you alot. With its Active you will do alot of damage.[code]
Now you should have gotten some kills and assist. So gold shouldnt be a problem. Now build Phantom dancer if you havent already, if you got it start building Guardian Angel. Start at Null-Magic Mantle if theres alot of AP and if theres alot of AD you start buying Chain Vest. After you done with your Guardian Angel, ofcourse sell Doran's Shield to make room for it. you got to make Youmuu's Ghostblade. You have alot of AS already, so this will help you alot. With its Active you will do alot of damage.

Nocturne is hell alot fun to play. Not only a great ganker, but also an escape artist if played properly. This is only a guide, no one is forcing you to build him as I do. I hope that you enjoy my build.

If you have any suggestions and questions you can leave me a comment :) Constructive critisism is a good way to learn, and I accept it like a man. No one is perfect!

Thank you for reading my guide to Nocturne, The Eternal Nightmare.
Hope you will try this out and find it usefull!