Hi, this is my first guide ever, I'm not a pro gamer, in fact my ELO is very low (I'm in elo hell), I don't expect you too like my build, but i will show it to you and i expect sincere opinion from you. If you liked my guide you can add me in LoL, and we can play a game together (i'm in EUNE)

Don't judge by only looking at my item build, read more about that build then judge

There might be some grammar mistakes because english isn't my main language

Pros
Extremely big damage
Easy farming
Can jungle
Has great lane staying power
Can solo vs. duo
Can clear caster minnions with lvl 4 Spirit Fire, which is great in solo vs. duo lane
Can mid (in lower Elo)
Can debuff enemy team with Spirit Fire
Is great in teamfights for his Ulti for eating enemy team alive
Great at pushing

Cons
"Squishy" early game
If you spam Spirit Fire to much you run out of mana fast
If you use wither on wrong target you may mess up a teamfight
Easy to overextend

Skill sequence is very situational for Nasus. If you are doing really good in lane and you need no pushing power just follow the sequence that i showed you up top, if your lane is being pushed really bad choose to max Spirit Fire instead of Siphoning Strike, if enemy Carry is overfed or building a lot of attack speed choose to max Wither over Spirit Fire ( but always make sure that you have it at least at level 4 for ganks on your lane)

If I know i'm going to have to take mid lane i will always max Spirit Fire first, and if i know that i'm getting a lane with a babysitter ( Alistar) who can ensure that i will stay safe while last hitting i choose to max out Siphoning Strike

Soul Eater (passive)
Nasus drains his foe's spiritual energy, giving him a natural 14/17/20% lifesteal. The lifesteal value increments at levels 1,6, and 11.

This is the main thing that keeps you alive in teamfights, lane, jungle.

Siphoning Strike (Q)
Nasus's next attack will deal an additional 30 / 50 / 70 / 90 / 110 damage. Siphoning Strike permanently gains 3 damage whenever it kills an enemy.

Try to last hit creeps with this ability only, but don't loose creeps if this ability is on cooldown, you need the +3 damage, but you need gold too. With sheen it gets really easy to last hit, if you have sheen and lvl 3 SS you can autoattack a caster creep and last hit him with SS

Wither (W)
Nasus ages his target, slowing their movement and attack speed by 35% and reducing it further by 3 / 6 / 9 / 12 / 15% each second for 5 seconds.

Use this to completely disable their carry (i.e. Ashe, Vayne, Miss fortune,..)
Use it to escape a gank by slowing the champion that has more CC
Use it to make a gank successful by slowing your target
Never use it on the closest enemy, there are champions with priorities for this skill


Spirit Fire (E)
After a brief delay, the target area becomes desecrated. Enemies in the area have their armor reduced by 20 / 25 / 30 / 35 / 40 and are dealt half of its damage initially and the other half over the duration -- initial 55/95/135/175/215 (+0.6 ability power) Magic Damage and 11/19/27/35/43 (+0.12 ability power) Magic Damage each second for the next 5 seconds

Rank 4 of this skill can clear caster minnions
Use this skill in teamfights to lower enemy armor
Use this skill to push and enemy turret
Use this skill to prevent enemys from farming/damaging your turret


Fury of the Sands (Ulti)
Nasus becomes empowered in the sandstorm for 15 seconds, gaining 300 / 450 / 600 health. While the storm rages, he drains 3 / 4 / 5 (+1% of ability power)% of nearby enemies' health each second (240 damage max per second) and converts it into bonus attack damage.

Use this skill in teamfights to eat enemys alive
Use this skill when taking baron since it deals % of enemys health
Don't use this skill under the turret, because if it hits an enemy champion you will draw turret agro
Use this skill when in 2v1 to change the tides of that fight
Never use it before teamfight, it's best to use it in the middle of the fight so that you know that enemys won't escape it before teamfight even started
Use this skill to save your life

I run Ghost and Teleport on nasus almost always

Ghost is an exceptional chasing/fleeing spell i.e. you start a fight and Wither the target, he uses Flash but doesn't get far away, so you use Ghost and he's a dead man because of your Phage/ Trinity Force, and for another situation you are geting ganked by an Udyr you use Wither on him, and activate Ghost and get safely to your turret. But if you are Flash player you can always exchange Ghost for flash

Teleport is great spell for backdooring at which Nasus is great, for geting back to a lane after being harrased, and after geting some items, and for doing a ward gank. teleport can be exhanged with a spell more usefull for team like Exhaust, Fortify, but other spells just don't go so well on nasus

But there's and exception for when you take Smite instead of Teleport, and that exception is when you go jungling (captain obivious strikes again :D) I wouldn't reccomend jungle Nasus but if you still want to do it it is viable

Dps Nasus is the build that i use the most, because he can do damage like in hell, he has survivability, and can 1v1 anyone.

Items

My core items on DPS Nasus are Trinity Force and Zeke's Harbinger. Trinity Force gives you the damage you need for farming up your Siphoning Strike, it gives a free on-hit slow, attack speed and some crit chance (with full build when enemys are on Spirit Fire you can crit over 1000(1k)). Zeke's Harbinger goes well with your passive to give you insane lifesteal, and it gives a nice ammount of attack speed which is enough with theese two items.
I buy them in situational order: I buy Trinity Force first if i don't lack lane staying power, and if i'm geting harrased pretty bad, then after Sheen and boots which are situational and will be explained later i get emblem of valour, because at this point I can heal stupid ammounts of HP

Now for other items they are all situational if the enemy team is strong in AD (they have more than 2) i suggest you getting Ninja Tabi, or if they are balanced/CC heavy always get mercury's threads, for your 4th item i suggest something defensive like Banshee's Veil against AP heavy team or Thornmail against AD heavy team or you can always go full damage and get a Bloodthirster, Infinity Edge, Last Whisper, 5th item is situational too if you lack damage get Bloodthirster/ Infinity Edge(if you didn't get it earlier), and if you want or need more survivability get Warmog's Armor or item you didn't get in 4th slot, and for the 6th slot i usually get Guardian Angel, but usually games take long enough for you to get your core items, and never forget Elixir of Fortitude and Elixir of Agility, get them when you have money leftover from your Sheen+ Boots, get them when you get Trinity Force anytime, they give you a nice boost in health, attack damage, attack speed, and some crit chance.

Masteries and runes

I run 21/0/9 masteries, because of the +4% damage dealt and crit damage

I use Greater Mark of Desolation because it gives you some early damage against enemy champions and makes it easier to last hit, i think this is the most usefull rune on all AD champions
greater seal of vitality because that +175 health at level 18 is quite nice
greater glyph of shieldin because magic resist is nice, and it's /lvl because you don't need much magic resist early game
Greater Quintessence of Health because health quints do pretty well on all champions

Farming

Now for farming, i know i'm repeating my self but it's the most important part of Nasus,

FARM UP YOUR Siphoning Strike

, if you don't farm up your Q, you are failing Nasus, and you should practice more on last hitting. With lvl 1 Siphoning Strike nasus deals 90 dmg, it's quite big damage so you shouldn't miss a last hit, and when you last hit your Siphoning Strike get's stronger by +3 damage

You can get blue easily when you have sheen, i usually do it at lvl 5-7, because if you get blue you can do some real pushing with spaming your Spirit Fire, and if you can take blue than the other creeps in the jungle should be a piece of cake

Gameplay

Early to mid game try to farm up your Siphoning Strike as much as you can, it's the most important thing to know as playing Nasus, if a teamfight starts and you're not there use your teleport to get into the battle, and if your teleport is on cooldown push that lane that you're in so hard that enemies would want to stop that teamfight and run to save their turret

Your main job at teamfights is to disable enemy's carry by using Wither on them, and take out their most fed player with few hits or to protect your carry for assassins, if you are still alive take out other enemies, because when their carry is dead there's almost no match for you, but never rush in first, you aren't the initiator, let tanks like Amumu, Alistar do the initiation, and only then you should come in

Late game/End game you should always participate in teamfights because you are one of the most valuable player/champion in your team, because you can take out their carry in seconds

Tank Nasus is build made for tanking and still doing some nice damage

Items

Like in all except jungling builds start off with a Sheen, it gives all the damage you need as a tank, then get situational boots, depending on the enemy team, if they are AD heavy pick up Ninja Tabi, if they are balanced/ap heavy/CC heav pick up mercury's threads. 3rd item is situational just like all others, if you are geting beat down by their AD carry get Thornmail or frozen hearth, if you are geting beat down by their AP carry get Banshee's Veil or Force of Nature, if you just want some health get Warmog's Armor or Sunfire Aegis(never run two Sunfire Aegis because their passive doesn't stack) which will provide you with some armor aswell.
4th item depends on what you got at 3rd slot, if you got some armor and enemy casters aren't doing much damage get health: Warmog's Armor or Sunfire Aegis, and if you bought magic resist and enemy AD carrys don't do much damage get health aswell: Warmog's Armor or Sunfire Aegis, if you got health item as your 3rd you should get some armor like Thornmail or frozen hearth, or some magic resist like Banshee's Veil or Force of Nature.
5th item should be armor if you got 4th as magic resist, or magic resist if you got armor, or you can always stick with health stacking which won't work very well
6th item i strongly suggest Guardian Angel
And last you should upgrade your sheen into trinity force if game lasts that long

Masteries and runes

As tank Nasus i run 0/21/9 masteries because dodge mastery goes well with your dodge seals, 46 health at start is really nice, and others to fully fulfill your tank role.
Now for runes:
greater mark of desolation because of easier farming early game
Greater Seal of Evasion because it goes well with masteries and is one of the best seals in game
Greater Glyph of Scaling Magic Resist because magic resistance is always nice, and /lvl because you don't need much magic resistance in early game
Greater Quintessence of Health because health quints are good on all champions

Gameplay

Early to mid game try to farm up your Siphoning Strike as much as you can, because it will be the only damage you will do at late game, if a teamfight starts and you're not there use your teleport to get into the battle, but teamfights should never start without you or your team is lost.

Your main job at teamfights is to disable enemy's carry by using Wither on them, and start attacking their most fed player with or go protect your carry for assassins, always rush in first in teamfights because you are the tank, you must always be in front of your teammates, Wither and go smash some faces, just don't forget to ping before engaging... You may not get kills, but killing isn't your job so it's ok, let your teammates have that gold.

Late game/End game you should always participate in teamfights because you are the tank, you must be there, if you're not there you are doing it wrong then

Jungle Nasus is the build i really wouldn't reccomend doing. But if you really want to, here you go.

Gameplay

You should start off with Cloth Armor and 5x Health Potion
Jungle route would look like this:, yeah i stole this picture from solomid.net hope they don't mind...
Start of at blue golem, have someone to pull/leash it, then you will have easier time killing it, then go to wolves, wraiths, and after you finish wraiths your smite should be up for red, after red get small golems and then you should be really low, so go B, get Boots, sight ward and some Health Potion, go thru jungle looking for a gank, and when you are ready for a gank inform your teammates by pinging the target. Lead with wither and if your team responds quickly you should get a kill or an assist.

Masteries and runes

As jungle Nasus you must roll 0/21/9 masteries or you will have trouble jungling
Runes:
Greater Mark of Attack Speed because you need the most attack speed you can get
Greater Seal of Armorbecause early armor for jungler is really helpful
Greater Glyph of Attack Speed because you need the most attack speed you can get
Greater Quintessence of Health because early 78 HP gives you safer jungling, or you can run Greater Quintessence of Attack Speed

Items

As jungle Nasus your items will be very similar to tank Nasus, except for Sheen, instead of Sheen get something like Atma's Impaler

AP Nasus should be never used in normal/ranked games, unless your whole team goes trolling

Items

For ap Nasus you start of like in a normal game with Sheen. Then you get Sorcerer's Shoes, build up Hextech Revolver, with this item your Spirit Fire and Fury of the Sands will heal you too, after Hextech Revolver you should finish your Sheen into a Lich Bane, now that you have some damage you will want some survivability so get a Rylai's Crystal Scepter it will provide you with some HP aswell as some AP, for more AP + survivability you should get Abyssal Mask because you are melee, so Abyssal Mask's aura will affect your target, then you should finish up your Hextech Gunblade, why not Will of the Ancients you may ask, it's because Hextech Gunblade and Will of the Ancients gives you the same Spell vamp, so Hextech Gunblade is superior in this build, and for your last item i would suggest Zhonya's Hourglass

Masteries and runes

For masteries you should go 9/0/21
And for runes:
Greater Mark of Magic Penetration because you need all the magic penetration you can get
Greater Seal of Scaling Mana Regeneration because you will be spamming your spells as hell
Greater Glyph of Cooldown Reduction because cooldown reduction is very nice
Greater Quintessence of Magic Penetration because you need all the magic penetration you can get

Summary

With this troll build you will be able to do some damage aswell as take some, but i repeat myself you should never do this build

This concludes my guide on Nasus

I'm looking forward into your votes and comments, if you vote up say what did you like, maybie you have some suggestions, if you vote down say what you didn't like and what should i change

Credits for taking their time to help me with good suggestions go to:

RepersentDK (EuNE)
urmamasllama (NA)

Thank you, for reviewing my guide, and commenting