Heavy use of mana, which is why i use Clarity and since I am a team player the use of Insight from the Utility mastery tree, can be a vital part of winning team fights so all mana users get mana refresh.

I try to last hit as much as possible with Siphoning Strike, and also jungle from time to time making sure I last hit every single mob with Q magic.

Nasus in this build is a slow starter and have to take care not overextending until lvl 6. He is also a very good mid champion with this build and I try to go gank early on when 1-2 lvls above the champions in the other lanes.

If played right and the Q magic last hit a lot, it is possible to get between 300-400 added damage from Q magic in late game.

He can crit. more than 2K in late game with this spec. and take down towers and enemy base alone in seconds with a group of creeps with him.

IMPORTANT! Buy Mana potions as much as possible when in base - I try to have 5 pots at all times when leaving base. This makes it possible to spam Q and E magic a lot when laning in addition to using the Clarity spell. I stop buying mana potions from lvl 14-15 only one or two if I have gold to spare.