This build is for those of you who want to help your team out very well mid and late game. You will have alot of health and decent resistances in both magic and damage. If you combine that with Nasus' natural life steal, you will have no problem in team fights. Even Madred's Bloodrazer will have little effect on you (usually :D). By the end of the game, you can sell doran's shield and buy another Warmog's so that your health regeneration + natural life steal will make you near invincible. There are other builds that are probably better for different situations, but this one is just a standard if you are ever unsure. Remember to build your Siphoning Strike at every possible opportunity. If your team is doing badly in turrets destroyed, just run at a turret and beginning striking it (be sure to time your siphoning strike correctly) and use your ultimate to bring it down faster.