Build Guide by RobertFreeman
Not Updated For Current Season
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Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
This build likes to abuse the fact that Karthus seems to be able to cycle through MP faster than any character I've seen. He can actually abuse the MP you get from one or even two maxed out Archangel's Staves, and wreck enemy lines with Defile. Spam Lay Waste on minions, or even just in thin air if need be, to push your max MP up faster. Since LW is kept at level 1 for a long time, you can spam it with no fear of running out of MP--except, of course, when you're killing six minions in two or three seconds of Defiling. Seriously, defile is an underused farming tool--just be sure to keep your max mana high, recall when you need to, cast clarity when you need to, and last hit plenty of minions without Defile on. Obviously, catch the Golem Buff when you can--not only is the extra mana regen very nice, but the huge cooldown reduction is great for Requiem. One of the best things about a Defile-heavy build is that in the level 4-11ish area, you can counter many ganks by turning Defile on, walling your enemies close to you, and hitting the Q button until 8 seconds after you're dead. You might need a requiem, but I've been ganked by 3 people, and, although I died, I killed 2 of them, req'd another enemy dead, and taken a buff. Ooh, that's another thing. When you nuke with Karthus, if you die at all, you technically die first--which means that, when you get the kill a few seconds later, you take any buffs either of you had with you.
As for the item build. I took the Tabi instead of mpen to give some much needed survivability to this build--and because they're cheaper, and as good as you will be at farming, this build can shred through money as fast as it does minions. That's why there's a pick in there, randomly. The Scepter gives you more survivability, is great for chasing enemies with defile, and allows you to slow enemies from across the map--pretty sweet. Sheen is kind of lame, but it's the best thing, of the ingredients, to get first on your way to Lich Bane, and while your inventory is running kind of high. End with Tabi, Archangel Staff, Scepter, Bane, Ring, Void. Yes, I know you get your mpen late (other than the mastery), but look at it this way: by then, you can see if your enemies have been bothering with much magic resist, and you can decide whether you want to go for a tougher option, like a Soulstealer, another Z's ring or Archangel Staff, or, if you're feeling really adventurous, turn your Pick into a Deathfire Grasp--which will turn your Karthus into quite the assassin. It has huge damage potential; with something like 600 AP, you'll do 51% damage to an enemy in one hit, for zero mana, and with pretty reasonable cooldown--and you already have a good portion of it built.
I don't find the Soulstealer a must, because of how momentum-based Karthus can be. if your team is winning, you can start raping face, Souleater or no. If your team is losing, you won't be able to do much good. You probably won't even be able to get a kill on most nuke attempts, let alone build up Soulstealer for a comeback. But, if you really are confident in your ability, an early Soulstealer (maybe about when you turn the tear into the staff) is perfectly viable. I would also say you could switch out Lich Bane, depending on how the range dynamic is going. I tend to only get a few regular hits in with Karthus anyway. But it's still a large damage booster.
Finally, you can try going with nothing but scorcerer's boots, Zhonya's ring, and Archangel Staves, which will cost you some of the more fun effects, like Rylai's health and slow, void staff's mpen, and the various oodles of fun from Lich Bane, but will give you ****-tons of AP--as it gives you, on top of other tings, 15% of your MP as AP (3% of that is from Z's ring affecting the other 12%). With 1000 MP + 400 per staff means 2600 MP + Karthus' base, 1368, Karthus has, for simplicity's sake, 4000 MP. That's 600, plus 45 * 4 from the Arch's base, plus 120 from Z's base, plus 25% of that, is another 375, so that's 975 AP. Plus 40 + 25% = 50 from your elixir, Karthus has 1025 AP, total, without runes or masteries taken into account. Requiem has 550 + 717 = 1217 base damage, defile does 110 + 256 = 366 base damage per second, and, to a single target, Lay Waste deals (120 + 308) * 2 = a whopping 856 base damage every second (assuming you don't have cdr masteries). With two skills, Karthus base damage output, without his physical attack taken into account, is 1222/sec. Talk about dps. With the boots, a couple of well-placed offensive masteries, and Zhonya's active, you become an effing force of nature (note: don't be confused, Karthus has no need for Force of Nature).
After you have your full item build, you might have some money left over before the game ends. You can spend it on the last four potions for AP/cooldown, health/AD, move speed/crit, and stealth vision--if you buy these while you have 6 items, they are applied immediately.
Keep an eye on Requiem's damage output at all times (or calculate it--it's 250/400/550 + .7*ap). Luckily, you can see your opponents' remaining health health by clicking on them, and you can see their items when you hit tab, allowing you to rather confidently predict when it will get you an across-the-map kill.
Pepper in pots for mana, ap/cooldown, and heck, even health, as desired. And of course, be sure to take mid.)