Hy guys, welcome to my "Complete nasus" guide :)
This is my first guide on mobafire, and i hope it won't be the last.
Nasus is a great champion and i enjoyed a lot playing with him, because he adact to my play-style: a play based on support allies, giving a lot of assist to teammates. Personally i'm more happy when i help an allie to kill a champion than when i kill a champion alone.
It's the principal reason for I choose to play with Nasus. If you want a game in which you want to do 25 kills and play alone, stop reading this guide, because Nasus is not your champion.

I will now entering you to a general analisy of qualities and difects of Nasus

Pros

- Great damage with Siphoning Strike at late game, if he farm well in early game
- Can slow enemies until 95% with Wither
- Incredibile ultimate, one of the best in Lol
- Great support to the team in offensive and defensive situations, he can do easily more than 20 assist every match
- He can solo lane very well, striking minions with Siphoning Strike and Spirit Fire
- The basic attach's passive guarantees good life steal already at the beginning of the game
- Affidable champion
- Easy to learn BASIC play with it, already from the first match i can use it

Cons

- Need a great early game, farming and farming and farming with Siphoning Strike, until the key "q" on your keyboard is broken
- Nasus, at early game, must refuse close combat with enemies
- For this reason, he must use his abilities, so look at mana, it's so easy to remain with very few mana
- He does not much kills, so you may have problems with buying items, especcialy at early game
- Needs an AD carry allie who can hit stronger and kill enemies: remember, Nasus is a support, an assistman, in football terms he must pass the ball to the striker so he can goal, he's not a great killer
- If he meet teemo in lane, he is f****d

Let's explain how abilities work:

Siphoning Strike --> This abilitie works exactly how a critical strike: in fact it's a powered basic attack. The total attack of this abilitie is :

AD = ( 30/50/70/90/110 ) + ( AD of basic attack ) + ( 3 x kills )

You can work only on the last two addends, by buying items and farming. When you kill a minion with the last hit with Siphoning Strike you gain 3 permanently AD in siphoning strike (basic attack doesn't increment). If you farm in a perfect mode, you can arrive doing a total damage of 600 or 700 in late game. Great damage, isn't it ??? :)

Wither --> This ability decrease movement and attack speed of a targeted enemy champion by 35% immediately and until 47/59/71/83/95% over 5 seconds. With Wither you guarentee a great support to allies,giving them the perfect help for killing the slowed enemy, but not only: in fact you also can save an allied or yourself, slowing the enemy and permitting the escape.
Therefore this item is great both in offensive and difensive situations.

Spirit Fire --> This ability can used in two different modes. You can use Spirit Fire to accelerate the advance on lane, killing minions faster. In fact this ability inflict a good initial damage to enemy units in the circle, reduce simultaneously them armor and do a bit continuos damage in the next 5 second. The other use is on enemy's champions: you can use Spirit Fire if you want to do damage to an enemy without get closer to him or you can use the ability in a close combat for reducing his armor and hit harder on it, when he's loosing continuosly life for the effect of Spirit Fire.
A great combination you can do is this: Use Whiter to slow enemy, then use Spirit Fire to reduce armor and then hit with Siphoning Strike. Great spend of mana, yes, but also great damage, and if there's one allie with you the enemy is surely dead ;)

Fury of the Sands --> This ultimate is maybe one of the best in Lol. Pushing "r" button you become an enormous grey dog around which rages a storm of sands and all the enemies take fear and run away XD .
Joking apart thisis a great ultimate. First of all you gain 300/450/600 life , then you deal magic damage to nearby enemies equal to 3/4/5% (+0.01% of AP) of their maximum health ( max 240 damage/sec ) and also you convert damage dealt to enemy in Bonus Attack damage ( 6,75% of damage dealt with Fury of the Sands ) . This ability works great when all champions are fighting closer and you are in the middle: press "r" and you can reverse the situation in your favour. I can't explain in words the sensation I feel when i strike all enemies around me doing enormous damage and killing them. I feel like a GOD DOG ;)

Ok, for Nasus i build a masteries with 15 Defense and 15 Ability.

With 15 points on Defense I can transform Nasus' health al lvl 18 from 2030 to 2339 : 309 hitpoints of difference are a great thing when you have to resist in a close combat with an enemy.
I can also increment health regen and reduce of 15% effectivnes of slows.

With 15 points on Ability I can solve Nasus' problems with mana, giving it +180 mana and +3 mana regen / 5 sec., but not only. Also I give him 3% Lifesteal and Spellvamp and 3 health regen / 5 sec for 400 maximum mana, so in late game Nasus can have + 12 health regen / 5 sec.

Don't work on attack masteries, focus on build mana and healt for nasus. Remember, he is a support, not a killer :)

Now i'll explain my rune's chooses

Marks: I take Greater Mark of Scaling Attack Damage for having a great AD at late game, when 9/10 there are no more schemes and all play mid 5 vs 5. You need then to have at least 200 AD, and this 9 runes give you a great help.

Seals and Glyphs: I use all theese slots to increase magic resist, because at level 18 Nasus' magic resist is lower than armor. So i take Greater Seal of Scaling Magic Resist and Greater Glyph of Scaling Magic Resist, because the items that i buy in game doesn't increment magic resist. Now a suggestion for you: don't spend many money to build your armor to 250/300, how can i see in several guides of nasus. Don't use 4/6 items to increase resist to enourmous values, it's useless, and now i tell you why.
I don't want to annoying you with grapichs and calculations, so i'll explain all simply.
Do you know that the formula for obtain the percentage of damage absorbed it's the same ???

Damage absorbed (%) = Armor Value / ( 100+ Armor Value )

Damage absorbed (%) = Magic Resist Value / ( 100+ Magic Resist Value )

Now i write you the increment of this percentage in determinate interval of armor/magic resist

from 50 to 75 armor = +9,52% damage absorbed
from 75 to 100 armor = +7,14% damage absorbed
from 100 to 125 armor = +5,55% damage absorbed
from 125 to 150 armor = +4,44% damage absorbed
from 150 to 175 armor = +3,64% damage absorbed
from 175 to 200 armor = +3,03% damage absorbed
from 200 to 225 armor = +2,56% damage absorbed
from 225 to 250 armor = +2,20% damage absorbed

Have you seen? The increment decrease at the growth of armor. From 50 to 150 you have an increment of 26,65%. Arriving at a level approximate to 150 you will absorb 60% damage, at level 250 you will absorb 71% . For 11% you must spend 3000, more or less, money that you can instead use to increas another statistic, AD or health or AB, what you want. In throut i prefer spend 3000 money to buy Bloodthirster than, for example, Frozen Heart.

Quintessences: For quintessence i take Greater Quintessence of Magic Resist for having a great magic resist at the beginning of the game. This help you when you meet an AP champion on lane.

Teleport --> I choose teleport because it permit Nasus to go also from the other part of the map in 4 seconds and in this mode you can save allies and turrets. I can't play without Teleport, a support champion must have this spell.
Heal --> I choose Heal because i can refill a bit of health to my nearby teammates ( and also to me ) and with the effect of Summoner's Resolve it give Nasus passively 5 Health each level, for a total of 90 Health al 18 level.

Ok, now you know how to build nasus and you also know his qualities and his difects, right ???
So i'll explain you how to play a very good game with Nasus, and i want to let you see the screen of maybe the best match played until now.




Yes, maybe you are thinking ... mmmmh, 5 kills, too few for a champion !!! And i gave you a bit reason, 5 kills are always few, even for a support like nasus, but look at the assist.
26 ASSIST ... few champions can do 26 assists, dieing only 3 times ( 2 stupid deaths ) and killing 5 enemies also.
This is your gameplay : kills when possible, die when strectly necessary and assist allies always, this is your priority.

Now stop speak of my games and enter in details :)

The game start. Buy Rejuvenation Bead and Faerie Charm and go on lane. You don't need now boots, you have already 350 movement, buy them later. Go to the turret, wait the minions and FARM.
FARM, FARM, FARM, you must only farm with "q" Siphoning Strike. Stay away from enemies, refuse every combat, focus on striking minions with "q". Initially it's difficult give them the last hit with Siphoning Strike, but if you start well the street will be only in descent and you can power Siphoning Strike easily and faster.
Unlock first all the abilities, Siphoning Strike (lvl 1), Wither (lvl 2) and
Spirit Fire (lvl 3), in order. Then unlock Siphoning Strike (lvl 4 and lvl 5) two times,
so you can farm easily and speedy. In the first 10 minutes you may arrive to a +90/+100 value from farming well.
Now you have to unlock Fury of the Sands and the game will start for you.
At first recall ( you might have recalled almost one time ) buy Spirit Stone and Boots. At second recall buy Ninja Tabi.

Now don't stay focus only on farming, start trying kill enemies with allie's help ( if you are 1 vs 2 let it go and continue farming ) and, this is very important, start looking the map frequently. In fact your mid game consist principally in supporting you teammates to resist when they are in difficulty and help them push on lane for let them killing enemies and turrets.
You have a very important role, you have to give good support to the team. Go where a turret is undefended and push enemies back, slow enemies so your allies can kill them easily ( so they can buy items faster and become stronger before enemies), save a desperate situation with Fury of the Sands, in short help, help and help. Don't risk your death following an hope of kill, don't feed enemies, play safe in the limits of possibile. I know that if you don't kill you don't gain money you don't buy items you don't get strong. You have to do the dirty work, like a halfback in football, you have to give the ball forward who can finalized the game. If you play good in mid game late game will be easily for all the team.
In this minutes you have to build Spirit Stone in Spirit of the Ancient Golem , then buy Rod of Ages. You now have greath health and sufficient mana for a great support to the team.
I want now to spend some words on Teleport. This spell is like water for you, you can't play without it. It allows you to go where you want in one moment, saving desperate situations. If you want you can buy the Enchanchement Distorsion for Ninja Tabi for reducing cooldown by 25%.
Remember continue farming, when you can ( now it isn't your priority ), so you can have a tremendous Siphoning Strike in late game.

Now you're going to the last part of the game. Now the game gets more confused, there are no more 2 champions top, 1 mid and 2 bot, now your team and enemy team push togheter when the enemy is weakness. Stop trying farming, stay with team and help them with your abilities killing enemies and defending their own life.
Now you have a problem. You haven't a good attack, so in a fray you don't have great chances, unless you use Fury of the Sands. In fact in a fray your ultimate is devastating, you give multiple attacks contemporanealy to all enemies around you, striking them and also killing them. Most of my kills derive by using Fury of the Sands.
So you have to buy no some attack items.
First of all buy Bloodthirster : it give you 70 AD and 12% life steal immediately, then for every kills it give you a bonus AD and lifesteal until the limit of 30 kills ( +30 AD and 6& Life Steal ).
Then buy Atma's Impaler: it guarantees you 45 armor, a 15% critical strike chance. Also his passive give you attack damage equal to 1,5% of your maximum health ( 50-60 AD ).
So now you can have 260-270 AD and you are ready to fight harder.
You have great health, great basic attack, great abilities, great mana, you can tell your story in this part of the game kill, finally, a ruthless killer.
Ok, i know that now i pumped you, it's time to go a step back.
Yes, you can now compete with enemies, but you aren't stronger than them. They will have more attack, attack speed, critical strike and ability power than you. So don't suicide in the conviction of being a SUPERDOG. You are still a support, and how a support you must continue playing.
Listen to me, look at the different situations and consider case per case the best mode to act.
If a champion is alone in lane with two enemies, run toward him and help him escape with Wither, or help hin to kill enemies, if they have no more life.
If a teammate is in the jungle and an enemy or two ambushes him, go toward your allie, hunt and go out at the right moment to surprise enemies and divide their forces, so you can save your friend.
If all champions are combacting mid in a closest range, go in the mix and use Fury of the Sands, then Spirit Fire and now strike with Siphoning Strike: if an enemy try to escape slow him with Wither. Left no one chances to enemies, try to kill all enemies with your team and scored an ACE. Then push and destroy all you can, like Gengis Khan ;)
In this last part of the game you can buy Phantom Dancer for increment the attack speed and having a great critical strike chance.
And if you have money to spend ( maybe not but if you do many kills you may have ) , buy items for increment attack and critical, so you can be still more devastating :)