Hi this is my first build i've made so don't take me too hard. Nasus is a champion that I love to play. He's a great tank, but also has great potential to do insane dmg. My build here is to make Nasus do decent dmg, but also enough beefyness so that he can have a lot of survivability.

Pros:
-Capable of insane dmg output with his Q
-Real tanky
-Has an amazing slow with his w
-Dog's r cool

Cons:
-No CC except W, which is single target
-Does not contribute much in teamfights compared to other tankies like Amumu, and Rammus
-Heavily reliant on farming
-No farming=GG for Nasus

- 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.

Absolutely an amazing passive. This is the passive, which can help you survive the laning phase for a long time. When your level 1, you already have 10% lifesteal! Lost half your hp? Well, just hit some minions and you'll get back in no time. Withandyou will be unstoppable in the laning phase.
- 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.

This is the skill that makes Nasus so powerful. At first it is very weak, but once you farm this skill up, you will do insane dmg. Remember this though, YOU MUST FARM YOUR Q OR ELSE YOUR DMG FOR THE REST OF THE GAME WILL BE COMPLETE ****.
- 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.

Wither is pretty much a 2nd exhaust. Because you have Wither you don't need exhaust. Perfect for slowing down your enemies or helping you escape.
- 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 (+20% of ability power) magic damage each second.

Great skill for farming. When you get a giant minion wave, just pop this right on top of them and down the drain they go. This makes Nasus a great farmer.
- 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.

This is such a useful ultimate! It has a built inand also makes your HP higher. Use this before you initiate.

One thing as a Nasus player is that YOU MUST FRIGGIN FARM. Nasus is completely useless if he does not farm. Sure he can run in and tank, but problem is that his dmg output is **** if u don't farm. You must last hit with your Q as much as possible so your Q can get farmed. With your Q farmed, your dmg output will go up by a mile. Make sure you last hit with Q or not. Farming is essential for every single champion in LoL, it's even more important for champions who depend on farming.

Mark of Desolation- Typical rune for any DPS champion. This will increase your dmg output by a lot.
Seal of Replenishment- Nasus has a really bad mana pool early game, so it is wise to get some mana regen runes.
- One of the best runes you can put on pretty much any champion. This gives 24 MR at level 18! That extra resistance could mean life or death. Greater Glyph of Magic Resist also works too if you want to focus more on the early game component.

Quintessence of Desolation- Same as Mark of Desolation.

Masteries are simple.
0/9/21

This is my favourite set-up on Nasus atm. The 21 points in the utility mastery helps Nasus a giant load in late game. The movement speed, summoner spell time reduction, CDR, mana regen, and many others help Nasus in many ways. The 9 points in the defensive mastery gives Nasus all the survivability he needs in early game. 9/0/21 is great too, but I do not think the 9 points in the offensive mastery is really worth it. The attack speed or CDR you get isn't amazing, but it helps. Archaic Knowledge helps your damage on your Fury of the Sands more, but your main damage should be coming from your Siphoning Strike. The critical strike is great, but I truly think the 9 points in the defensive mastery is worth it as the nimbleness proc can save your life along with the dodge rate. The extra 6 armor helps your early game sustainability much more as right now the metagame is calling for tanky DPS top. Overall, I prefer 0/9/21, but 9/0/21 is just as great! It is all personal preference.

9/0/21

This mastery set-up gives an amazing late game as all these masteries help out Nasus so much. There is CDR, summoner spell time reduction, movement speed, mana regen, and more! The offensive can be great because the extra crit can get you that damage to kill your enemy or to last hit. Archaic Knowledge boosts your ultimates damage. My second prefered mastery set-up.

0/21/9
If you are truly not confident with this mastery set-up you can just go 9/21/0. This makes you exceptionally tankier, but does not help out your late game phase as much.

For summoner spells I go for Ghost and Teleport
Ghost- I believe ghost is such a great spell for pretty much all the champions. It's great for chasing enemies or escaping from enemies. If you don't like ghost, flash would also work great, but in my opinion I think ghost helps a lot more because of its shorter cooldown.
- This is mostly personal preference. For me I love to get teleport as it helps your solo topping much easier if you are not experienced. It is not just noob friendly, but it is also a great split pushing spell. When the enemy team is all top and your bottom turret is pushed, you can easily Teleport down there for an easy tower. Nasus is a great split pusher due to the power of his Siphoning Strike+ Sheen proc on the towers.

Ignite- Getting ignite is great because when enemies are on low life, you can use ignite to ensure the kill. It also works great for champions who have a lot of hp regen like Dr.Mundo. It's overall a great spell.
Flash- The metagame summoner spell right now! This is a great spell for escape and chasing. It is a high CD spell, but it helps alot sometimes, maybe even more then Ghost. At the moment I prefer this more then Ghost, but I'm sure that will change eventually.
Exhaust- Exhaust is an amazing spell to slow enemies and rape them, but I don't think it's as viable on Nasus. Your W already gives you a whopping amazing slow, so Exhaust might be a little bit redundant. You can get this spell if your not sure if you can chase and kill your enemies, but overall I don't think it is required for Nasus.

Starting Build-

Doran Shield- Great starter item for Nasus, gives you good hp, armor, and hp regen. This gives you great survivability and is highly recommended.

You can start withandx5. Only do this if you are not confident enough to survive without HP pots. Honestly, with Nasus' passive I don't think you need HP pots because your lifesteal and Doran's Shield will just do the job.

Core Build

Mercury's Treads- I think these shoes are great for Nasus because it can lower the CC that ppl put on you, meaning a slow can last shorter so you can own them. I almost ALWAYS ALWAYS get these on almost all of my champions because these boots are the most versatile boots. If you don't like these shoes, you could always grab aor. Another great item is, someone recommended me this because it helps the CDR of Nasus' Q. Now that I think about it, that 15% CDR actually helps Nasus quite a bit. It makes your Q more spammable!
Sheen- This is the core item of Nasus and the one item that can make your dmg go BOOM. All you have to do is farm your Q then use your Q hit and rape.
Trinity Force- Same applies to sheen, it helps your dmg output so much.
Warmog's- Gives you amazing survivability. Great for Nasus.
Atma's Impaler- With your Warmog's you will have a lot of hp. So if you have an atma's, your dmg will go sky high.
- One of the best items ever. The shield can be a real life saver sometimes. Whether it be a stun or a nuke that could kill you. All this is blocked with Banshee's Veil. This gives great magic resist along with HP and MP making this an exceptional item. Note though- In my build I do not have a lot of MR
so if they have a AP carry that is getting fed or they have a lot of AP then Force of Nature would be a great replacement for Frozen Heart or [Banshee's Veil]]

- Frozen Heart is such an amazing item because it gives you a great debuff to enemies along with lots of armor + CDR. CDR means less CD on your Q meaning more damage :D.

Situational Item's-

Force of Nature- If your enemies are just plain AP, then FON is for you! It gives great magic resist, which will prevent casters from hurting you as much.
Thornmail- If your enemies are just plain AD, then Thornmail is for you! Along with it's 100 armor and its passive. Auto attackers like Tristana and Master Yi will die from hitting you.
Aegis of the Legion- This great item can not just help you, but also your allies. It is also very cheap compared to most of your items so this is definitely a viable pick.
Stark's Fervor- Gives you great attack speed along with 20% lifesteal! With Nasus' passive, which gives you 20% lifesteal at lvl 11, you will have 40% lifesteal with your Starks and you will be able to regen your hp in a flash.

Simple skill sequence for Nasus. Get your ultimate whenever you can after that get your Q whenever you can. We can debate on wheter we should get Spirit Fire or Wither first. In my opinion I would get your W because wither is pretty much an exhaust. It is so helpful for helping you escape and chase enemies. Your E is good to and if you max this before your W you would have a much easier time farming and it also lowers enemy armor. The choice is yours, but my opinion stands with getting W first.

I like to take solo top with Nasus, as it allows you to farm up your Siphoning Strike compared to duo bot lane. Duo bot lane is simply just not recommended. Depending on your partner that is. You could go support bot lane, but it would be better to give that to your AD Carry. Mid can be a good option, but normally that is where the great harassers are such as Brand, Caitlyn, etc. These guys simple just outrange you and make you unable to farm. So the best place is usually solo top lane as that puts you up against bruiser melee like champions such as Garen and Cho Gath. In early game all you got to do is FARM FARM FARM, just keep on doing that for the next 20-30 minutes and you will be godlike late game.

Around here you still should be farming because the more farm the better your Siphoning Strike becomes. Only in crucial team fights should you join. Other then that, just keep on farming and you'll be fine.

This is where you shine. If you successfully farmed up your Siphoning Strike you will be godlike. Your Q will hit for loads of damage and you will also be exceptionally tanky. What you must do in teamfights is just go for the main carry. Ulti in along with your team and head straight for the carry and chop him down.

So this concludes my build of Nasus.

Please try not to be too harsh on me as this is only my first build and I still have much to learn.

Thanks for reading my build!
It would be very helpful if you guys could give me some feedback and constructive criticism so I may improve my builds in the future.

I will try to update this as much as I can. I'll also try to add more parts in the future.