Welcome to my Nasus guide! Nasus is underrated by many people and doesn't get seriously, but if played correctly can do some serious damage, taking down turrets in 10 to 15 seconds. With this guide you should be able to carry your team to victory.

Please know that Nasus' main damage skill requires you to last hit with it, so if you aren't very good at last hitting you should probably not play him.

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. War was never more than a breath away, as others of his kind craved to enslave the people and claim totalitarian sovereignty. In the midst of a heated battle, just as Nasus was about to slay his treacherous brother Renekhton, he was summoned to Runeterra. It didn't take much to convince him that Champions were needed to fight against the injustice here and he took up a place in the League of Legends. These days, he is the Keeper of the Sands, feeling most at home in the crumbling ruins of the Shurima Desert.

''The Keeper of the Sands, though contemplative, is not to be trifled with.''

Pros:

-Amazing carry
-Can do huge damage
-Slow helps chase down or run away from an enemy
-AoE farms minions fairly easily and helps get your last hits

Cons:

-Mana problems
-Slow only effects one enemy
-Without last hitting you can't be your full potential

I find it's easier to play Nasus and get those beloved last hits when you're in the middle/solo lane, but the double lanes work fine as well.

Do's:

Ignite, a favorite of many players, is a great finisher to get a kill on a Champion that is running away.
Ghost can be used to easily chase down an enemy player.
Teleport can move you between lanes quickly. If you decide to get this spell instead of Ghost, replace the Haste mastery with the Spatial Accuracy mastery.

Maybe's:

Heal can help you early game or in a team fight, but because of Soul Eater it's not really necessary.
Flash can get out out of danger or closer to the enemy quickly.
Cleanse can get the CC off of you quickly and get you back into the fight or run from it.

Dont's:

Everything else. They don't really help Nasus out much.

Soul Eater is your passive. it gives you natural lifesteal, which is why I don't get any lifesteal items.

Siphoning Strike is the skill you need to last hit with. It should be the second skill you get, but maxed last. The reason for this is because the base damage increase isn't all that much, and the thing you want out of is it the bonus damage you get when killing enemies with it.

Wither is your CC skill. It is the last skill you get besides your ultimate but should be maxed second. The attack and movement speed reduction already can help you and your team chase or run from an enemy, but the bonus after a few seconds can help you ensure a kill or no death.

Spirit Fire is your farming skill, and therefore should be your first skill maxed. You can quickly kill off a wave of minions with this, and it also allows you to use Siphoning Strike quicker. When using it for laning, wait until the enemy minions meet your minions, then use Spirit Fire and get as many of them inside of it. It has a large area, so you should be able to fit the melee and range minions in there. This technique will get the most money for you.

Fury of the Sands is your ultimate and should be gotten whenever you can (level 6, 11, and 16). With it, Nasus gains health and has an AoE around him, dealing percent-of-health damage to enemies, making it great for damaging tanks.

Nasus can be used to initiate an enemy or come in after the fight begins. What you'll want to do is lay down a Spirit Fire on and behind the enemy a bit, unless they're pushing your team back where you should lay it in front of them. Then slow their squishiest Champion or DPS and have everyone focus on them. Use Siphoning Strike as often as possible, or if they are about to die wait until you are assured the kill so that Siphoning Strike will gain bonus damage. If at any point you fall below 1,000 health during the fight, use Fury of the Sands. You will gain health and start dealing AoE damage. You can also get in the middle of the enemy and use it if they are bunched up during the fight.

Start out with Sapphire Crystal, a Health Potion and a Mana Potion. Because of Nasus' low mana, Sapphire Crystal will give you a boost and will build into Sheen. The Health Potion and Mana Potion will keep you in your lane as lost as possible.
Next, get Sheen. This will give you bonus attack damage after using a skill and will build into Trinity Force.
For boots I like to get Boots of Swiftness so I can be as fast as possible, but Berserker's Greaves can also work.
If you are able to build Trinity Force the next time you're at the shop, do it. If not, work for Malady. After that, get the other. Malady gives you huge attack speed, some ability power, and has some nice passive effects. Trinity Force gives you a bit of everything, a chance to slow your target, and keeps Sheen's passive while making it better.
After that, if you are still having mana problems, get Nashor's Tooth, but if not get Phantom Dancer. Nashor's Tooth gives you attack speed, cooldown reduction, mana regen, and ability power while Pantom Dancer gives your attack speed, movement speed, and critical strike chance.
By now you should have huge attack speed and critical strike chance, so your last item should be Infinity Edge which will give you quite a bit of attack damage, critical strike chance, and increase your critical strike effectiveness.

Once you have enough attack speed and bonus damage on Siphoning Strike, you can try backdooring a turret. Wait in the enemy jungle near the turret you are going to try to backdoor until most of the enemies are on your map and away from you. Then just go out and beat that turret to shreds, using Siphonig Strike as much as possible and ignoring enemy minions (or you can put down Spirit Fire to get rid of them if they are really bugging you). If you're not done with that turret but the enemy is coming for you, you can no longer see them on your map (wait a second or two until your minions reach the minions in the lane they were in to see if they're not just pushing with their minions), or your health gets below 600 without 1 or 2 hits left on the turret, it's time to get out of there and finish the job later, but that turret should nearly be down.