I have played nasus for about 100+ games now n he is definitely my favorite champion so i decided i should make a guide for it

First of all, NASUS SHOULD NOT BE A FULL TANK! Guides that make nasus with all tank items and no AD or AP stuff will make nasus absolutely useless in ganks he will just stand there and watch others die. ALSO! note that the item are not permanent and it can change depending on situation so go look at the item explanation section!

Second, Nasus is minion dependent, if you dont farm and build your SS, you will be pretty much useless in your team.

Pro

AMAZING if farm well
can lane for very long time after getting some mana/mana regen
DPS + Tank
nuke hits very hard
aoe armor reduction + slow
Mid-Late game champion
Versatile, can go high Armor or high Magic Resist

Con

can't really chase after opp get out of wither
needs alot of minion kills
squishy until lvl 6+
mana hungry until frozen heart

I put
Greater Mark of Desolation for armor penetration this seriously increase the damage output in your SS
for more mana regen which gets rid of your mana hungriness
magic resists, since you are getting mostly armor items, it is good to have some magic resists.
flat hp for longer survival

I put 1/21/8 since nasus is going dps he will have items that deal high damage therefore he will need some defence skills during entire game to tank some damage while dealing massive damage back. And i find that nasus needs a lot of health n mp regen and he needs to level up fast thats for the 8 in utility. AND 1 FOR EXHAUST YEH!

Exhaust
Since Nasus has wither, not really a good CC as u can tell since they would just ghost away after the 5 second, well reduce his speed even more with exhaust! 8sec!

Ghost
Nasus is not a fast character. Can't chase can't escape, with ghost anything can happen.

I see Exhaust as a must but Ghost can be replaced by Teleport a great spell to get move around the map in a sec. or Flash same thing as ghost, to chase or escape but this goes through walls!

Passive:
This is definitely a great passive, free LS! that means you dont have to worry much about losing health as you can always farm some minions and return back to full health in no time.
Nasus drains his foe's spiritual energy, giving him a natural 10/15/20% lifesteal. The lifesteal value increments at levels 1,6, and 11.

Siphoning Strike:
Nasus's nuke! This is the skill that determines if you win or you lose. Please do yourself a favor n go up to the minion with low health and click Q. If you farm well (at least 250+ bonus dmg) you should have a no problem killing squishies or opponents carries. 110+ AD+ AP+ 250= probably around 700+! haha my best was +498! This is also the reason why i max Q first for an early start in funding.
Nasus strikes his foe, dealing damage and increasing the power of his future Siphoning Strikes if he slays his target.
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.
Cost 20/25/30/35/40 Mana
Range 300

Wither:
Nasus's CC skill. Its like a weaker version of exhaust! Use it when chasing enemy or use it when running away. Add with your summoner exhaust skill together is an 8 second slow, DAM! ALSO! it slows your opponent's attack speed so use it to initiate fights or during fights. You can level this skill before SF if you r doing very well and dont even need team to gank.
Nasus ages his target, decelerating their movement and attack speeds over 5 seconds.
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.
Cost 100/100/100/100/100 Mana
Range 700

Spirit Fire:
Some people may mistaken this skill as a damaging skill but it isn't well not really, it does like half 1/10 of a bar.... 50hp? anyways the main use of this is to either scare your opponent from thinking it does a lot of damage or the main use, ARMOR REDUCTION! at lvl 5 its 40 armor reduction which is great against all champions. Reduce their armor and wack them with Q. Throw it in team fights, 1vs1 or any situation when you are attacking your opponent. Dont throw it when your running ull slow ur self down. Level this skill up before wither if you are ganking alot with your teammates.
Nasus unleashes a delayed spirit flame at a location, dealing damage and reducing the armor of enemies who stand on it.
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 20/34/48/62/76 (+0.2) magic damage each second.
Cost 70/85/100/115/130 Mana
Range 650

Fury of the Sand:
Nasus's ultimate. This is a great ultimate for almost any situation. During team fights, whip this sh*t out and it steals your opponents' healths automatically n turn it into your bonus damage. It works in any situation when you are at low health. For example at lvl 6 u r laning but this guy is trying to kill u. you have around 1 bar left while he has full bar, whip this ult out n boom 1/2 health bar for you to lane 5 more mins or if your good n use ur passive to LS, full bar! kill him!
Nasus unleashes a mighty sandstorm that batters nearby enemies. While the storm rages, he gains additional Health and drains nearby enemies' max health and converts it into bonus damage for the duration of the skill.
Nasus becomes empowered in the sandstorm for 15 seconds, gaining 300/450/600 health. While the storm rages, he drains 3/4/5 (+0.01)% of nearby enemies' health each second (240 damage max per second) and converts it into bonus attack damage.
Cost 150/150/150 Mana
Range 20

Basically, all of nasus's skills work together during team fights. Initiate with wither, Q him, spirit fire, ult, QQQQQQQQQQQQQQQQQQQQQQQQQ till dead.

Basically boots for increase speed to 395 and then the added 25% AS for faster farming. With this item you can basically stop buying health potion as you can just farm minions to regen health.

This is a great item for Nasus's SS cuz every time u do a autoattack, your next attack increase by 80% 3 sec cooldown. That is a huge increase during mid-late game difference of 400+ dmg. You also get 25 AP and 250 Mana.

Probably one of the best item for a tank. It is a balance between armor and magic resist. +30Armor n +39 MR while giving aura to teammates. Also increases health, less squishy.

You probably won't be able to get this the first time you go back so probably get a first. +99 Ar +500 MP, -25% CDR, and it also reduces enemies attack speed by 20% around you. Great item in general, gives you more armor to get rid of squishiness and more mp for mana hungriness. NOTE: You should get this item before if you are doing well (not dying and have scored a few kills or assists) if not, get Aegis first.
A great item to start your rampage. it is all rounded for Nasus, 30 AS, 30 AD, 30 AP, 15 crit, 250 Health, 250 Mana, 12 Movement, n some slowing passive. However, the best thing is that instead of 80% increase base dmg, has increase of 150%!!!!!!!! WOW! basically a crit every 3 seconds. After getting this item, you can pretty much tell the result of the team, if you are surviving= win, struggling= not clear, 9 turrets down= nawwwwwww

40 AD, and the best thing about this item is its 40% armor penetration, great against tanks. along with the armor penetration becomes amazing.

This is a great finishing item. 55 AD, 30AS and this reduces your opponents armor by up to 45!along with Last Whisper n your armor penetration runes, that Rammus of theirs will seem like he forgot to bring his armor onto battle field. you will probably be the one running up to the tank when hes at 1k health and 1hit ko him leaving him calling you a hacker.

replaces : I would only do this when the opponent team is really Magic heavy, with at least 3/5 of them doing ONLY magic damage. For example, + + get or you WILL die fast.

replaces : Happend to me a few times when the opponent don't really have mostly carries with low health, armor, magic resist. Therefore, get more AD and LS as well, this item stacks up to 100AD and 25% life steal.

replaces : When your opponents are HEALTH tanks such as or when you see that at least two of them have gotten health items such as

Early

I always start with a and + This will give you +200 mana when you want to SF the minions. From lvl 1 to lvl 5 remember NEVER CHASE unless you have a clear advantage, at this stage you are slow and weak. Just stay in lane and keep on last hitting minions with SS. Even if that annoying is shooting you from afar, don't try to kill her. Go back a few pixel and wait for low health minions to SS. Remember, not many ppl check your minion kills so if you have high bonus on SS, you can kill a carry in about 5 seconds. Just laid back for a while and increase your SS. You should probably go back base when you have 2k+ gold (for me around lvl 6 or 7). After that I go for a to upgrade myself to 395 speed and with the +25% AS it will help farming and passive. And i upgrade my crystal to I then buy u can buy 1 health 1 mana if you feel like you are struggling to survive in lane. At around lvl 6 or 7, I start going for my opponents (unless they are tanks) start pushing them back as now you should have no fear of dying. Even though you may be a squishy in others eyes, your should prove the differ. Farm more until you have money for . Also pop your any time you feel pressured.

Mid

With + + You are now starting mid game at around lvl 7 or 8. You can start ganking with your teammates leaving your lane. Remember the sequence of skills, -> at where they r going -> LIKE MAD! you can anytime you feel the need to such as when it seems like your team need a boost or when teammates r dying or just to finish off faster. You should have after ganking a few times. You should have no mana problem after frozen heart. However, I will always get the blue golem buff if i can as it will allow you to stay in lane and continue ganking cuz trust me, your health bar wont lower much. REMEMBER! continuously kill minions with when you can, since theres no limit to its +3 bonus why not get it as high as possible.

Late

This is after lvl 13. You should be able to get pretty soon this gives you a well-rounded increase. The game usually ends a few min after i get trinity, around lvl 15 or 16. However, if the game continues on get the next 2 items. When you are at low health after a gank, go farm some minions instead of going all the way back to base as your passive n hp regen should recover ur hp in no time. Gank with ur team using your ult Basically just get the killing order down and remember that tank is for you to kill not others! And also, the last two items are situational items, and may change depending on your opponents. As far as changing goes, don't go for any AP items.

is a champion that needs ALOT of minion kills early and mid game. If you have other champions who are minion kills dependent, try to switch with some one else or it might result into one of you being great while the other below average.

-I don't typically farm with cuz it is a waste of mana and it doesn't really help your SS. I only SF to keep champions away.
-I usually stay in a distant and when i see a minion at half bar, i run up do 1 auto attack and to kill it. Afterward i go back to safe distant and wait for cooldown. (Do this till lvl 9, max SS)