There are also several other builds, the first one i wrote is if you do well and dont get focused ( even if u get focused, you have an awesome passive ;D ), the other one is a more tanky build but also good...


Some Tipps:

-as karthus you should always try to land your [Q] on single targets to deal bonus damage
-try to position yourself in the middle of the teamfight because your [E] deals tons of damage
-you can also build an early tear of the godness, it giv4es you mana and combined with a chalice of harmony you dont need a bluebuff
-if you fail hard on lane, do wolves and wraiths to get your money and buy a kages lucky pick
-spellvamp can really help you out to stay on lane
-karthus' early damage is hughe, harass your enemie with your q
-you can easily farm the ranged minions by spamming your [Q]