Inspired largely by Nasus - The Demolisher. The main difference is I make him a little less tanky and a little more off-tanky by getting him Tiamat right after Sheen. The much-maligned Tiamat you can think of as Doran's big brother - an item that isn't super great, but good enough that you don't necessarily have to sell it if you put big-tag items in your other slots. Usually I like Philosopher's Stone for MP5 and HP5, but Nasus needs all the help he can get farming hard early to be a presence later on. Tiamat is sort of just barely enough AD for Nasus, since he mostly builds as a trinity tank and isn't going to go crazy with Infinity Edge anyway. Ultimately, I find the ability to farm a little more gold helps him snowball in a way that balances out an occasional lost Siphoning Strike.

If you upvote this, go upvote The Demolsiher, too. If you're the only non-squishy on the team, then this build isn't quite tanky enough, and something like The Demolisher should work better. But I've put some thought into some general-purpose tips that may be worth reading in any case.

Items are up to you, but it's nice to rush Sheen. Alternately, you can get Rejuvenation Bead, Faerie Charm and a few potions. The good thing about Faerie Charm is that you're a little closer to Philosopher's stone if things really go badly. Teleport synergizes with Sapphire Crystal, though, letting you delay the MP5 a little bit if you want by filling up a bigger mana tank fairly often.

Spirit Fire at 1 to check bushes. Wither at 3 if you can wait that long - if you use Exhaust before 2, you should probably take Wither at 2. In any case, once you have Siphoning Strike, you're ready to start building it.

You don't necessarily have to have Sheen to farm up your Siphoning Stike, I've discovered - though it is quite true that the Sheen effect stacks with Siphoning Strike, making it your main one-hit weapon. Early on, Tiamat is as good for Siphoning Strike as Sheen is, but the regeneration helps more than the flat mana of Sheen. Of course you'll want both ASAP.

Good players know that they should try to deny Nasus, but you might have some luck using Spirit Fire to simultaneously weaken minions and to harass enemy champs. Run in so that you can finish off that minion with Siphoning Strike and you're golden.

Of course it's nice when they leave you alone and you don't have to use Spirit Fire just to farm. In that case, just try to last hit with Siphoning Strike. Note that pressing Q resets the auto-attack timer, making a noticeable difference when your ASpd is low - finish off that minion with the old one-two: land one auto-attack, press Q almost at the same time, and then quickly finish off with RYAAUUH!! Overleveling Q is a good idea if you can last-hit with it almost as often as it goes off of cooldown.

Also, I like to siphon-farm the tiny minions that accompany the buffs on your side of the river, and sometimes the wraiths, wolves, and baby golems as well. Don't do this and annoy your jungler if you have one, though. If Q is leveled up, run in circles to avoid killing without Q in some circumstances.

One more note: You can farm Siphoning Strike better with Sheen than with Tiamat, depending on the circumstances. If you are left to free-farm, it's rather easy to last-hit, wait around, and then last hit the next one. But if a lot is going on, you might not get more than one or two minions per wave whether you have Tiamat or not. Regardless, I put Tiamat after Sheen in the main build because sometimes I find that stage of the game sometimes favors the burst damage and slightly better Siphon farming.

Know that nightmare when you run but you don't go anywhere, sand is blasting you in the face, and an enraged jackal is running after you? It's kinda like that for them. Fury of the Sands is best used when you need the extra 600 health, like when you don't want to have to disengage from a fight you'd otherwise have to. Wither and Exhaust can be used back-to-back if they don't die the first time. Once you have Trinity Force, you can get a few attacks on them and probably get a Phage proc on them during your main slow(s).

Flash might be a good choice, especially if you're quite good at leveling up Siphoning Strike. Teleport is nice for letting you split-push and swap lanes. Doing the Siphoning Strike one-two with Tiamat lets you either save mana on Spirit Fire, or it lets you push that much faster, depending on how you use it.

Using Spirit Fire offensively

EDIT: They changed this skill a little since I first wrote what follows. Half of its damage is dealt all at once, which means that you would prefer to actually hit them with it initially if you can, compared to how it was before. This has to factor in to your timing and placement now.

This can be a tricky spell, as there's a slight delay. Basically, you have to either anticipate where they're headed, get them stunned, or use it to separate enemies and create dilemmas. If two enemies are somewhat far from each other, then place Spirit Fire so that one has to run through it to get away, and the other has to run through it to help out. You can also use it on a region enemies have to run through to get to an imperiled ally.

Even if you only just graze them with a half-second of Spirit Fire, they get the armor reduction. If you can Flash behind them for a Siphoning Strike, go ahead. Zeke's Harbinger will exaggerate the effect even further.

This build is too squishy to really tank hardcore during Fury of the Sands. If there are just 2 or maybe 3 enemies around and they can't CC you, then maybe you can get by on your ult and some lifesteal, but for the most part, you don't want to get focused too much with this setup. 3100 health isn't incredible. Better teammates should keep them off you to some extent, though.

The last item can vary, I suppose: Randuin's Omen, Black Cleaver, Guardian Angel, Youmuu's Ghostblade. The last one if your team has a pure tank and isn't that AD-heavy, but I usually pick Nasus to help out AD-heavy teams in the first place. I'd lean Guardian Angel or Randuin's Omen to stay tanky, especially if you don't have a tank; the latter is a better utility choice if you're not likely to be focused much. If you have a pure tank on the team and an AD carry, then Black Cleaver + Spirit Fire + Zeke's Harbinger is pretty deadly, but you'll need yourself, the AD carry, and the tank to work together to properly wreck faces.

You can eventually sell Tiamat for one of the others once your Q is farmed up, but watch your mana in team fights.

Pros:
* Focuses on Siphon-farming
* Lanes well
* Hard-hitting offtank
* Carries around two slows
* Great when paired with an AD carry and a tank
* Pushes hard
* Sort of decent temporary tank with Fury of the Sands, but don't get crazy
* Side-jungling early-mid-game strongly encouraged if you have no full-time jungler

Cons:
* Not a tank
* Item-dependent
* Weak late game if denied early