Alright, so if you're here, it's because you red the title and will read the guide. Good. This build is made to follow a very specific gameplay.

I'll TRY to keep this short, but it's really difficult.

Get doran's shield, which is VERY useful, incredibly useful. This will allowed you to go farm farm your Q with being able to take minion/champion damage. I usually don't even pay attention to the harrassing of my enemy laners because I don't care about getting kills. All you want on the early game is to FARM and STAY ALIVE, that's all.

RUSH THE SHEEN! Why rush the sheen? Simply because it makes your farming job SO MUCH easier and, when you get this, you can actually counter-harass AND push towers. The enemy will quickly learn not to get too close of Nasus.

BOOTS. You have the choice between the Ninja's Tabi and the Mercury's Treads. This is, obviously, depending on the enemy team composition. Lotsa AP/CC > Mercury. Lotsa AD > Ninja.

BUILD THAT TRINITY. Trinity makes your Q even more OVERPOWERED and gives you other benefits such as attack speed and slowing attacks. This is perfect to chase down an enemy, and having crazy damage.

WARMOGS. At this point, you're either in mid or late game. You'll need warmogs just for the sustainability, so you don't need to recall as often, and also you just need to get tankier in general. Enemies will attempt to focus you because your Q hurts like a *****.

ATMA's. Obviously, when you get warmogs, you want Atma's for it's passive. Give you a great beneficial Attack Damage and makes you more tanky + crits.

GUARDIAN ANGEL. If the enemy still maintains the focus on you, Guardian Angel's your Guardian Angel. They'll focus you less, AND you get useful armor bonuses, making you more tanky.

REST. Your choice. I usually win before this point, but if you get here, try to get tanky items such as Banshee's Veil, Force of Nature, Sunfire Cape, depending on the enemy team comp.

SIPHONING STRIKE, SIPHONING STRIKE, SIPHONING STRIKE, SIPHONING STRIKE, SIPHONING STRIKE, SIPHONING STRIKE, SIPHONING STRIKE, SIPHONING STRIKE, SIPHONING STRIKE, SIPHONING STRIKE, SIPHONING STRIKE, SIPHONING STRIKE, SIPHONING STRIKE, SIPHONING STRIKE, SIPHONING STRIKE.

Good game.

If you can farm this REALLY well, hoping your opposing laners aren't good harassers, you will win. If you have no jungle, take the top lane for the 2v1 = easy farm. If the enemy solo lane is easy, just take it, only weaknesses are probably all AoE spammer champions.

Farm is Nasus's middle name...or his last name, maybe both. Don't care about kills, don't care about anything else except FARMING. Farming and, obviously, surviving. If you can pickup a kill at the same time, GREAT, but focus on farming. Just watch out for the ganks.