This is my first build on mobafire. Its just my opinion what items, runes etc. nocturne need. HAVE FUN

The best runes are Armor penetration or Health.

Pros:
- Great Ganker
- Great farmer
- Great chaser
- All abilities can be used offensively and defensively
- Good jungler
- Scary Ultimate


Cons:
- Squishy early/late game
- Vulnerable to CC, pretty weak escape mechanisms (Banshee veil will help you)
- Mana problems in mid game

In my opinion, Ghost is a must for Nocturne. It works great with Duskbringer, both offensively and defensively. If you are a Flash fan, you're welcome, it will be helpful too. Personally I don't like Flash because of it's long cooldown.
I take Exhaust as second. You can always use Ignite (then you will have to change Cripple to 1 point in Archmage's Savvy in the offense tree) or Smite if you want to jungle (then change Cripple to Plentiful Bounty).

If enemy team has like 10000 stuns, fears, exhausts etc., or you are simply focused all the time, you can take Cleanse. With Banshee's Veil and Shroud of Darkness you can block 3 enemy spells!

Other Summoner Spells you might use:
Clairvoyance - might be useful with your ult to show, for example, enemy jungler and jump on him, or someone who escaped gank and is recalling near his turret. It's also very useful for supporting your team, scouting Dragon/Baron Nashor or simply checking brushes if enemies are missing.
Teleport - can be useful to gank, for example by teleporting on a ward or Teemo's mushroom in brush.

What you should never take:
Heal - You dont need it because your passive ROCKS!
Clarity - No. Take blue buff.
Rally - WHAT?
Fortify - Nah, tank should take this
Revive - What revive? what for?

Items are at the top ^^

You can start to harrass at lvl 2, when you have 1 point in Duskbringer and Unspeakable Horror. Start with Q, run to your target, use E and auto attack like there is no tomorrow. Use Q again when available. But never miss it! If you'll miss your first Q, the whole combo goes to waste. If you have problems with skill shots, practise vs bots or your friends on custom games.
At lvl 4 combo looks like this: Q, W (to prevent any disables from enemy), E, auto attacks, Q and so on.
Enemies will be like "OMG I just used my stun, WTF?! OMG he is hitting even faster now, someone help me, please! :("

And now... yes... this is what you were waiting for... lvl 6 and Paranoia !
Find a good prey for yourself. Use your ult, then use your W (yes, before using R one more time!!), then dash to your target, Q, E, auto attacks, Q and KABOOM, KILLING SPREE!
And why W before dashing to your target? If enemy is wise enough, he will prepare his disable for you.
For example: enemy Veigar is pushing top lane. You wait in the brush to jump on him, use Paranoia and dash on him. OMG what happened?! Oh ****, Veigar used his stun before you reached him... damn it... And he used Flash to get away...
I forgot this several times and trust me... it can end up even worse than just with not having a kill...

Remember to make some defensive items because champion with only dps items sucks!!!
AND ALWAYS REMEMBER TO USE. Its the best for chasing, 1v1, running from enemies, if your ghost is on CD.