I based this guide off of a post by TBM CheeseyFries.

He's the top ranked Karthus main out there, so I'd take his word for it. And this is essentially a transcription of his post. Flame me or not, idrc.

Thread: http://na.leagueoflegends.com/board/showthread.php?t=659583

Side Note: Don't mind the numbers box up top, the list of items only includes 3 you will use, the rest are your discretion based on what is listed in the items chapter. Actual ability power will be several hundred higher.


CheeseyFries:

Hey everyone, here is my guide for Karthus play. Please upvote if you like, downvote if dislike.

First, why should you read this guide: Well, I'm fairly high ELO, briefly hitting gold in 5's before losing it, and am also familiar with the competitive scene. I frequently play with most of the big names, so i feel safe in saying my Karthus guide is viable for high ELO. Karthus is my #1 main, and I have almost 500 ranked WINS with him, so I'm familiar with all his mechanics.

Anyways on to Karthus!!!!

I find standard caster runes work best, so 3 x hp quints, mp5 yellows, mpen reds, and flat CDR blues.

With masteries + flat cdr blue, you get 14.89% CDR, which, when coupled with a late game blue buff, will essentially max out CDR (39.89)

9/0/21. Standard caster for the most part. Spec up to 15% mpen in offense. In utility, get full points for less time dead+ champ experience.

I run flash so I get improved flash. If you run ghost, spec into ghost taking one point out of time dead, and if you run teleport, then spec into tp.

I run three possible combos flash/ignite, flash/ghost, flash/teleport. My standard is flash/ignite. I normally will solo mid, and flash should give enough protection in mid from ganks. Ignite I find just ends up being the most effective 90% of the time.


If I'm stuck up in top lane, I will run ghost to avoid jungle ganks.
Against kite heavy teams (Ashe/Janna, etc), I might also run ghost for better chasing; it's situational.


As for teleport, against teams with a backdoor presence, TP is very useful. Ignite/ghost/TP all work well, its honestly your preference, but take flash no matter what.

Items are ALWAYS situational, so what I describe here is just one general build I will use. Remember to always adjust in-game accordingly! Also remember to ward and against poke heavy teams, always keep 1 or 2 hp pots on you.


Start: Sapphire crystal+ 2 hp pots.

Grab boots 1 as you next item, then build a tear.
If you are getting ROCKED in lane (mainly vs Kass and aggressive corki's) then get a catalyst for the hp/level up bonus, but tear is honestly made for Karthus. You spam your q so much that you can max it by 30-35 min in most games.

Next get a Rabadon's, picking up the needlessly large rod asap.

I normally get sorc shoes after my needless, but sometimes first, and sometimes not until after my deathcap (situational!).

Then finish your archangel. Aim to have both these offensive items done by 25 min.

If you got a catalyst, then build RoA after deathcap.

--DO NOT build a mejais on Karthus. Only time to get one is if you are super fed, in which case you can build AD, because you will win anyway. You need to be unafraid to die with Karthus, so don't do things like buy oracles/stacking items, unless you are so far ahead it won't matter. You lose stacks instantly upon death, and you tend to ult after dying so in close games, you will never get the full benefit of the Mejais.--

oror
After Archangel, get a void staff if the other team is stacking Mpen, banshees if you are insta-dying, or Zhonyas Hourglass vs burst heavy teams.


Pick up a Rylais if people are running away from you too fast after you die.

It doesn't really matter, although I normally get void staff after deathcap and archangel. With archangel/rabadons/void you will do truckloads of damage, pretty much more than anyone else in the game.
The rest is just situational itemization. Elixir up as needed.


On rare occasion i.e. if the game goes 60+ min, and we need to push or defend real well, I will sell boots and buy lich bane (it gives some lolzy burst, and the proc is ALWAYS up).

Ok now the fun part! Game play:

Levels 1-5: Spam Q. A lot. Use it to farm. Use it to poke. You need to get a feel for the delay on it, and try tp oredict your enemies movements. It takes practice, but it is most of your damage, so it is worth mastering. If you can last hit (with or without q), you will never run out of mana. Try to hit single targets with your q, either minions (for better last hits), or enemies (for great harass). With ignite, and your 2 hp pots, feel free to trade hits in lane. You will out damage them. If they try to fight, just kill them. Try to avoid using your e, unless its clear its a fight to the death; its does only 30 damage/sec, and drains a lot of mana. Similarly use your wall with discretion becasue it takes a lot of mana and is your only cc. If you fall behind in harass or come out on the wrong side of a fight, just farm from safe distance with q, as no one can stop this without exposing themselves to an easy jungle gank.

Levels 6-10: I try to stay in lane till 20 min when I have a deathcap, tear, and boots. Just keep farming, it should be very easy, and keep up the harass. Make sure you always have enough mana to be able to ult a sidelane. Generally at 6, you are weaker than your opponenet because they now have an ult, and while your ult is great if they run at low hp, you can't use it mid combat. So play cautiously at least until 7, and ideally until 9.Your q has 875 range so just about any harass they try is easily countered with a few well placed bombs, and if you can get a lead, you might be able to finish them off. It depends on the opponenet/jungler/etc, so know your own capabilities. more than anything else.

Levels 11-15: Mid game should begin around now, so hopefully you have some decent items. If you are playing mid, you will be needed for the first dragon fight, and once you are 11, you should try and get your team to go for dragon. By 11, your skill-set does a lot of damage, and, thanks to your passive, in the event of a full team fight, you will likely win. Remember, once the initial burst is gone, to get into the middle of the enemy team. If they run, pick them off with your q, and if they fight, mow them down with your e. Use your wall to slow carries, and to essentially deal true damage to them. If you die, do as much as possible for the first 4.5 seconds, then press r. If your team understands the concept if finishing team fights, you should win, and hopefully you + your ad carry just got several combined kills. REMEMBER TO BE AGRESSIVE. Get in people's faces, get up close and personal, get your aura of doom flying everywhere. You are Karthus, you don't care about dying, and if you do, you are taking them with you. And then spawning first too ;-). Also, keep farming mid-game. Once you are 13, you can use your e to wipe minion waves in a flat 3 seconds, so you should always be best in cs, or very close to best. Farm at all possible non-essential times, as you need gold to finance your expensive and awesome items.

Levels 16-18: Late game. By now you hopefully have your core 3 items of deathcap/archangel/void staff. Your basic strategy in team fights remains the same: use your q to poke, and get into the enemy team when the fight starts. Keep in mind, however, that lane game, no matter how much survivability you buy, you will explode if you charge into the enemy team too early. Try and wait for some initial burst to be used. If it is clearly being saved for you, then buy a zhonyas (defile works through it), and enjoy 2 seconds of extra life, which often ends up buying you a lot more as people waste so much stuff in the 2 seconds. Also, late game is where your flash really shines. You probably can't just walk up to the enemy carries any more, so flash up! Kill people! Pop zhonyas! Triple kill! Press r! Penta kill! You get the idea!

Keep in mind that Karthus has more damage out put in team fights than ANYONE else, so abuse it. Your ult is a nice finisher, used mostly after you die, although sometimes you can work it in during initiation, it depends on the game/fight. If you buy a lich bane, you can force team fights, because you can now poke turrets. For 1/3 of their hp a hit. So either people fight you, or no more turrets. But make sure you have a LOT (600+ ) of AP or the investment won't be worth it. You can also take Barons with extreme speed. The biggest thing about late game Karthus is having the killer instincts to know when to charge into the enemy team, and the best way to develop that is practice. As a general idea though, charge in about 1-2 seconds after main initiation, and make sure you are fighting carries. Your late game damage output comes from your q+e more than your r, so make sure you can hit moving targets in team fights, and make sure your e button works. Don't be afraid to die, and you will end up winning, and your team will love you forever and ever.

So that concludes my guide. Long, but hopefully entertaining and informative. Anyone wishing more detailed tips should add me in game (CheeseyFries), so we can do a custom or a normal sometime.



And that concludes my transcript. Keep playing Cheeseyfries.