This guide will more show you how to build Nasus and not how to play him because he is really easy in my Opinion.

"The enigmatic creature known as Nasus came to the League from a faraway world, and served as part of a vast and learned desert empire. There he was a respected and enlightened individual, having been made the Keeper of the Great Library. However, he was also part of a race of animalistic creatures that served as the rulers and protectors of the people. Unfortunately, there were others of his kind that believed they were more than protectors. They were under the egotistical delusion that they had ascended to become gods. War on Nasus's world was never more than a breath away, as these deluded others sought to enslave the people and establish a totalitarian sovereignty. In the midst of a heated battle, just as Nasus was about to slay his treacherous brother Renekton, he was pulled through the cosmos to a summoning circle in Runeterra.

At first angered that he had been taken just as he was about to cripple the enemies of his people, Nasus' advanced intellect won out when he heard the pleas of mercy from the summoners. He learned that Runeterra was also filled with its own brand of injustice. This danger was no less threatening than what he had fought against at home, and champions were needed to protect the people of this world. Heeding the call, Nasus chose to take his place in the League of Legends, knowing that his brothers and sisters would carry on the fight back home. These days, he is the Curator of the Sands, feeling most at home in the crumbling ruins of the Shurima Desert. However, recent disturbing news has reached the Keeper's ears - rumors that perhaps his brother had not in fact been left behind. If this were the case, the destruction of Renekton would quickly become Nasus' main priority, before this world too faces the threats of his brother's forked tongue and endless ambition.

The Curator of the Sands, though contemplative, is not to be trifled with."

Why pick Nasus?

Nasus is one of the strongest toplaners in my opinion. His Ultimate can surprise your enemys that try to dive you or think they can easily kill you. You can pick Nasus or better should pick Nasus if you need some Ap but also a tank. Nasus is very easy to play but strong at the same time.

Pros

-Great Sustain
-Nice Ganks
-Easy to play
-He is a Dog
-Nice Towerdives
-Hard to gank

Cons

-Mana Burner
-If he gets zoned, its hard to get out
-Easy to Poke/ harrass with non Skillshots

You harass your enemy with your "E" and "W" Combo. If u feel safe to kill him. Go in for it. Nasus is really strong before he reaches lvl 6 but after lvl 6 he can just smash his enemy. If you get Problems on your lane just ask your jungler to gank. Nasus slow is in most of the cases a sure kill for you or you jungler. Try to farm up your q and spam it in a fight with your enemy. If your enemy is Nidalee or someone else with great escape skills, it is harder to kill him but not impossible. Poke him/ her down and then go in for it so that your enemy must go back or die. Use your "E" like a Skillshot. The Explosion does more damage but dont underestimate the DOT. When Nasus reaches lvl 8/9/10 farming is easy. So if you get outzoned at the beginning it is much more easy to farm up.

When the first Teamfights start, use your ult when you have about half of your health and when you are in the Center of the TF. You will heal so fast up, that the enemy will stop attacking you and going on your adc. If your enemy does this, slow him and kill him with your Q. Sounds easy, it is more easy ingame. At the beginning of the Tf, place your "E" so that you hit most of the enemys with it, and try to hold the enemys in it. Your "Circle of Doom" will help you win the Fight because your carries do more damage.

If you are full equipped, feel free to iniciate the Fights with your enemys. Nasus is just a beast in the Late game. Its very easy to get kills, and you do so much AoE Damage that your Team should win every Tf without high losses. Your main aim in the Late game is tanking the Damage and protecting your Carries. If you open the fight, hit either one of the carries with your Q or the Bruiser that focuses one of your Carries.

This is my first guide and I wanted to try my best. I would appreciate it if you give Feedback on what is good and what i can do even better.