Karthus Build Guide by Dotter

Very nice, personally after the rabadon's though i would go for a void staff. Then i either go for more archangels, or rylai's depending on whether or not i need the survivability.

Deathsteak:
Void Staff is in the optional and I often use it, since it gives more damage on the entire eneny team, rather than more AP that only damages the squishees alot.

Lol, running from karthus early game, why would anybody do that? :p
Especially Ashe. If she hits you with her crit and one volley the moment she spots you, you have about 150 hp left.
I feel Karthus benefits more from a ROA early/mid game, because his AP ratio's are ******* bad anyway. Spec more into AP later in the game for his ulti's relatively high AP ratio.
I hope this helps, sorry if you think it's bs.

Didn't read other comments to see if someone already said this but I'd recommend Will of the Ancients over Hextech Gunblade. Especially on a caster-heavy team.

Sadly Not:
Omg fail xD The item I meant to put in was actually Will of the Ancients. xD
Karthus doesn't need AD anyways xD

I tried this build and it did wonders but I would suggest the Soulstealer right after Sorcerer's shoes. By this time you should be around level 6 and as soon as you get your ultimate, your kills and assists come pretty easily especially in team fights. If you're doing a 3v3 and you pop your ulti close to the end, all 3 of them usually die and you got 3 assists/kills, depending on when you time it.

Hycinix:
The Soulstealer is only in the optional, since some people don't like Snowball items.
You are completely right, however, I haven't tried him in 3v3, so I dunno about that.

dude dont know what they say in ratings , your builds are awesome . :D

Also, I usually get Tears of Goddess a little earlier so I can use my E without much problem :) also I spam q alot so it goes up fast