In this guide I will talk about being a tanky Nocturne and how it is very effective. With this build you will be able to take damage as well as deal alot.

Pros:
Hard to kill
Can turret dive more effectively


Cons:
Slow start
must be a little fed
No mana at the start

Frozen Mallet or Thornmail: theses 2 depend on who you are against if there are 3 melee take thornmail unless they have been feeding then get the hammer and chase them down to get fed.

Other items can be exchanged if needed but keep the Warmog because it is your main tanking item.

For my runes I like to go with the mana regen ones first because when playing Nocturne you use up alot of mana like most champions. They are also very effective in late game because then your mana never runs out if you also get blue buff. The glyphs that I recommend getting are harder to get but in the end it is worth it because no matter what you say in the end runes make a difference on how games will go at 20+ content.

Here is where it gets interesting I like to get Offensive masteries to help my damage. my next few are in Utility because of the ghost and the regen is also very nice. Change the ghost and exhaust talents based on the spells you want.

Q. With this you can hit the enemy and it leaves a trail where they go. It can also be used to escape. On this trail you move faster.
W. This shield blocks ONE enemy spell within a few seconds. This can be used to block Ashe's arrow to save an ally or to block Corki's missiles.
E. This is your fear with this you can save an ally or destroy a foe.
R. Now with this you activate it and it removes the enemy's ally vision and if you activate it again and click on a champion in your range to dash to and deal damage.

for this you just get Q first no matter what then depending on who is in your lane you get shield if they are ranged with a distant melee and the fear is the are melee and the ranged is shy. With the Q make sure you keep the enemy low and your mana about at 50% so that you have it incase you need to escape.

Ghost: Great for chasing and escaping. A must for Nocturne.
Exhaust: you can chase them and kill them even faster with this.

Alternates
Ignite: Great way to dps them down.
Smite: ONLY if you are going to jungle.
Flash: If you are not a fan of ghost.
Heal: Can be good if your team is in need of it.

Follow this as a starter for a tanky Nocturne add on to what information I have given you and you should be able to be a great off-tank. Please do comment with tips and questions.