Karthus is a very unique champion, most commonly played in the Midlane as an AP Carry.

Unlike most of the other AP Carries, his skillset is not so much about bursting single targets down with a combo, but more about dealing massive DPS-AOE magic damage with a powerful global ultimate on top of that and a passive, that allows you to do damage for a few seconds after death. He can be described as one of the strongest Lategame champions in the game, but you pay for that by having a rather slow early game. However you can farm pretty well with him.

I'm very far away from being a high-elo player or stuff, but I think I play Karthus pretty solid and he's been my favorite midlaner for months now. In this guide you'll find tips and tricks for laning and teamfights as well as some items to consider for different situations and how to annoy enemy-Karthus players. This is my first guide here.

Marks: Greater Mark of Magic Penetration.
no exceptions.

Seals: Different possibilities here.
Greater Seal of Armor - good against AD heavy teams or AD-bruiser midlane.
Greater Seal of Mana Regeneration - always nice to have some Manareg.
Greater Seal of Scaling Health - a solid defensive option.
Greater Seal of Scaling Ability Power - an offensive option. Not too good imo.

Glyphs: Greater Glyph of Scaling Magic Resist against AP-Lanes
other options may be:
Greater Glyph of Magic Resist - flat MR versus strong earlygame-nuke-casters
Greater Glyph of Scaling Ability Power - an offensive option. Better values than corresponding Seals.

Quints: Greater Quintessence of Ability Power
in 95% of all cases flat AP should be ideal. Consider Greater Quintessence of Magic Resist (or an early Negatron Cloak) if you know you will meet LeBlanc. Spellvamp may also be viable, but I didn't test that a lot yet. I can't see any other options.

Pretty much straight forward for AP Casters: 21 in offense for the Ability Power and Magic Penetration. Whether you spend the remaining 9 points to the Defense or the Utility tree (or a mix of both) is pretty much up to you. Some Movementspeed/ManaReg might be nice, but some HP and Magic Resist too. I mostly prefer the Utility, but this is not carved in stone and also depends on the enemy you will lane against.

You really want that Flash, as it's your only gapclose. Not bringing Flash is like an invitation to gank the s*#t out of you. Lategame it is also important to get into the right position in teamfights.

You have some options for your second spell:
Most casters bring Ignite to finish of enemies, but I don't think that suits Karthus well, as you have Requiem. However Ignite might be useful in some situations e.g. against heavy selfheal-Champions as Ignite also brings a heal-reduction or Champions, that can dodge Requiem by one of their Abilities.

However I prefer Teleport in most cases to be mobile and be a even bigger global presence, especially when laning against roaming-heavy champions like Twisted Fate, Evelynn or Katarina). If you get Enchantment: Homeguard early, the Teleport it is even more powerful.

I also see lots of people bring Exhaust on Karthus, which is a solid option to win 1on1-fights, have a teamfight-utility or just to survive easier.

The Revive/ Teleport strategy

This is kind of a "troll selection" called suicide karthus, which can be successful, if the enemies does not adapt to that strategy. Lategame it is pretty mighty, as you can teleport back into an ongoing teamfight dealing tons of damage for a second time.

However there are 2 reasons, that makes me think this isn't viable if you play against good enemies:
1. Revive cooldown is sooooooo long
2. You give up Flash, which will cause your Early game to be a lot harder and potentially feed your enemies so you won't even see the Lategame.

All in all I can't recommend to choose those summoners, although it certainly works against decent enemies, because you have the element of surprise on your side.

Choosing the right starting items on Karthus isn't a no-brainer on Karthus. In season 2 I almost always went for boots and pots, but with the season 3 changes there are new possibilities. Solid possibilities are now:

Sapphire Crystal and 2x Health Potion

pro: builds quickly into Catalyst the Protector.
con: no wards

Crystalline Flask and Health Potion + sight ward

pro: Sustain and vision.
con: you'll have to wait a bit longer for major items

Cloth Armor and 4x Health Potion + 1x Mana Potion

pro: solid start against AD-Bruiser midlanes, builds into Seeker's Armguard
con: not useful against AP-Caster midlanes.

no regular major item, just a couple Health Potions, Mana Potions and sight wards

pro: awesome lane sustain.
con: you'll have to wait a bit longer for major items

Boots and 3x Health Potion

pro: some sustain, some quickness to dodge enemy skills/ganks
con: no wards

Practice to get your lasthits with Lay Waste and auto attacks. You can pretty easy get your lasthits under or near the tower. Dont push your lane, as you will get ganked and as Flash is your only gapclose this might result in a kill for the enemies. If your lane is pushing and its too dangerous to farm, ask the jungler if you may do wraiths and wolves.

Your Lay Waste gives vision. Use that to check brushes, never, I repeat, NEVER facecheck them. Also Sight Wards are worth their money. Buy them.

Normally you should'nt use Defile for creeps early. You may push your E for a second or two if you miss a minion otherwise, but turn it off afterwards, as you will get out of mana if you spam it. Normally you dont get oom too quickly because of your Defile passive.

Ask the jungler for the second blue buff (and all the following ones as well). You can solo them by midgame easily without the jungler. You don't really need ganks in early game, if you dont get zoned too hard; it may be better to send the jungler top or bottom and once you hit level 6, you can give them the additional 150-200 damage needed to make the kill via Requiem.

However if your lane-enemy is bad enough to get harassed by your Lay Wastes early on, a gank might also be successful as your Wall of Pain has a nice slow you can follow up with some Lay Wastes. However don't expect to get kills on your lane early on.

Against most lanes you can easily get your 120-140 Creeps in 15 Minutes (if you are really good and/or take wraiths and wolves from time to time too even more).You dont believe me? Watch that Karthus played by Froggen making a creepscore-record with 300 creeps in 23 minutes. Play Video

Dont be an a*#hole and take kills, which your team gets anyways. I repeat: DON'T. Your cooldown on Requiem is too long for that and your team might need your ultimate's damage a minute later to gain a double kill, then doing baron and win the game of that advantage.

Also, you better know which champions can dodge spells (see chapter "Counterpicks against Karthus"), and check the enemy inventory for scumbag-items like Banshee's Veil, Hexdrinker, Elixir of Fortitude and Zhonya's Hourglass.

If you don't want to embarass yourself, dont cast your Requiem alive with nearby enemies. Either look for a safe spot so noone can interrupt you, or cast it when you are dead with your passive triggered. Don't wait more than 3 seconds after you are dead or you wont have the possibility to cast it anymore.

While you did all you can not to die in laning phase, you can actually die now sometimes. Not on purpose of course, but your role is to go deep through their lineup, damaging everyone with Defile and spamming Lay Waste at their Carries, while your Wall of Pain slows them and lowers their Magic resistance. When you have a solid build, you should be able to survive that for quite some time and when you finally die, you trigger your passive and deal damage for some more seconds and then cast your Requiem if needed.

It's essential not to go for "all-in teamfights", when you are either out of mana or your Requiem isnt up.

Don't get caught alone, as you will fall pretty quick in an 1vs3+x situation, even if you built up a little tankiness. However if it happend and you are dead, cast your Requiem if its up, even if you know you won't get a kill, so that your team can manage the 4vs5 easier.

Your Lay Waste and both ends of Wall of Pain provide vision. Use that if you don't have vision for Dragon or Baron and you aren't sure, if the enemy team is doing it.

Although you want to go deep into their lineup to reach their Carries, you shouldn't go in first. Let your bruiser/tank engage or wait for the enemies team to engage on your team to avoid getting isolated from the rest of your team and die too quickly. Its okay to use Flash offensively in teamfights to get into Range for their Carry. In most cases its not useful to use Flash away from an enemy team, except you got caught alone and can flee with using Flash over a wall. If you brought Exhaust, use it on their AD carry or a fed Bruiser. If you chose to buy Zhonya's Hourglass make use of its passive while they are focussing you.

If you die, but the enemy team is aced, your job is done. However if you manage to survive, Karthus has good pushing potential because of his huge AP and fast waveclearing.

With enough Mana you can Solo Dragon easily, however if possible do it with your own Jungler securing it with Smite and also make sure you have vision around the Dragon. Same for Baron Nashor, but obviously never never solo it in a serious game.

As Karthus is one of the very few champions, that pretty often get their fullbuild because of his farm and kill-secure-potential, buy Elixir of Brilliance and Oracle's Elixir if you have extra Gold to spend at the end of a game. Elixir of Brilliance can be even useful before having Fullbuild when an important battle isabout to begin (e.g. around Baron Nashor)

Enemies run double AP
Enemies stack Magic resist
Your team runs double AP / Enemies tanky as s*#t
Maximum AP Build

Core items

Rod of Ages

Sorcerer's Shoes (later: Enchantment: Homeguard)

Rabadon's Deathcap

Mostly I even buy it in that particular order, but if the gold-amount does not quite fit, I swap Shoes and Rod of Ages sometimes. An early Catalyst The Protector is helping you a lot to survive your lane.

Very good items

Rylai's Crystal Scepter

I love this item on Karthus, although most people don't go for it on Karthus. You may argue your W is already a slow and the Item-passive isnt really needed, but the slow percentages stack, and your Lay Wastes will slow enemies too, so its like a Red Buff for AD-Carries. With 500 more HP your are harder to kill, reaching more than 3000 HP together with Rod of Ages at Level 18, while still granting a nice amount of AP.

Zhonya's Hourglass

Awesome item on Karthus, as you gain Armor, AP and that passive. Use it while your Defile is active and when they desperately try to melt your HP down while you are standing in their lineup.

Liandry's Torment

A mighty item as it gives you HP, AP, MPen and an on-spell effect doing aditional Damage to all your Lay Wastes. I really like building this as the fifth or sixth item.

Situational items

Void Staff

Situational item if the enemies stack Magic resistance (scumbag Runic Bulwark). If they don't, your shoes + Liandry's Torment and/or Abyssal Mask might be enough penetration, as you wont gain any defensive Stats by this item.

Will of the Ancients

Spellvamp is massive on Karthus and this is the only way to get it besides Spellvamp runes. (Don't even think about Hextech Gunblade, you are not Akali)
I think it works best against tanky teams, while its not as good vs teams with a lot of squishy High-Damage-Dealers. If your team has an AP Toplaner (e.g. Vladimir) maybe you are lucky and get the aura from him, while you can pick up something else, or you decide to run the Double-Wota-Strategy.

Abyssal Mask

If you needed an early Negatron Cloak to survive that Veigar or LeBlanc burst, it's a solid item to go along with. But normally there is only one AP Char in a team nowadays and you also have to get lots of HP to make the MR actually useful, so I dont get this item in most of the cases currently. If the enemies are playing double AP (like Jungle Fiddlesticks or Rumble Toplane in addition to an AP-Mid) it's an option as well.

Archangel's Staff

I don't really build this often, as it gives you nothing besides AP and Mana, and I like my Karthus being a little more beefy and with Rabadon's Deathcap we already have a pure AP-item. Some might see it as a solid option, because its easy to get the stacks for that Seraph's Embrace and Karthus' Manapool is naturally high, so you gain lots of AP by this item, but mostly there are 5 major items I'd rather have. Still not a bad choice.

Guardian Angel

I built this sometimes as the last item for fun when I had a good game, while the rest of my team was struggling, just to make sure I can stay alive as long as possible. As you dont gain AP by this, you give up some damage potential though, so its really just a situational pick.

Mejai's Soulstealer

just no, except you want to stomp Bots or poor Lowlevel-Guys. You'll die in teamfights and lose all that sweet stacks you may have gained. Also the item does not give you any defensive stats at all.

I saw a few people jungling Karthus, and while its possible to survive the jungle with adjusted Runes/Masteries and taking Smite, I don't suggest doing it, as you won't farm up in the jungle as good as you do on a solo lane, and your ganks are not more than decent. Yes you have Wall of Pain and maybe and early redbuff, but your ganks are a joke compared to those of Maokai, Xin Zhao etc. pp.

Another reason you should'nt consider doing Jungle Karthus in serious games is, that you are pretty much f*#ked when they steal your first Blue buff. Amumu players will know that feeling. You aren't a decent counterjungler as well, not to mention the problems you get, when they counterjungle you.

Lane counters

As already pointed out, Karthus early game isnt the best, so lots of midchamps can be considered counters for his laning phase. However with some practice and skill you should be okay to deal with most of them and farm you into later stages of the game.

Learn to dodge CC-skillshots like Ahris Charm or Luxs Light Binding. You have to know your enemies skillset to have a chance. Always try to imagine what you would do as the enemy player to kill you. And then act in a way that prevents him from doing so.

Basically there are 2 ways to counter your lane pretty hard: champions with high mobility and single target nukes like LeBlanc and Kassadin and champions that can harass you from a huge distance like Xerath and Nidalee. I think Veigar counters him too with his ultimate, as he can pretty much one-shot you when he has stunned you once.

Also the new AD-Bruiser-midlane-meta with mobile champions like Jarvan IV or Lee Sin mid is nasty, as you do like no damage to them early. As said before, consider an early Seeker's Armguard to deal with them as good as possible. And farm like a undead skullhead. Oh wait... you are an undead skullhead.

how difficult it is not to die/farm well against common midlaners

(based on personal experience, of course it depends on the enemies build, playstyle and skilllevel a lot)

Nightmare
LeBlanc, Kassadin, Veigar, Xerath

pretty hard
Ahri, Akali, Diana, Ezreal, Fizz, Gragas, Jarvan IV, Katarina, Kayle, Lee Sin, Lux, Malzahar, Master Yi, Nidalee, Orianna, Talon

moderate
Anivia, Annie, Brand, Cassiopeia, Evelynn, Fiddlesticks, Galio, Malphite, Mordekaiser, Morgana, Ryze, Swain, Syndra, Twisted Fate, Viktor, Vladimir, Zyra

Other lanes

Soraka is said to be a huge counter for Karthus because of her passive and Ultimate, however I think this is only true for the early to midgame, as she most likely won't stack AP and you can outdamage her Wish in the Lategame by far. Also she has a very long cooldown on her Ultimate, so it won't be always up, except she is reserving it only for you.

Basically all kinds of heals and shields are soft counters, if you want to grab kills via Requiem, but its not like Requiem is all you have, like some flamers seem to believe ("noob karthus only R OMG QQ")

As I already said, there are some Champions that can dodge spells or quickly recover lots of Health and you should'nt waste your Ultimate, if you are not sure if they still have them availible. Those include Sivir, Fizz, Morgana, Vladimir, Nocturne, Elise and the Ultimates of Kayle, Zilean, Tryndamere and Poppy.

Also the passives of Blitzcrank, Volibear and Mordekaiser can cause your Ulti to fail.

Besides that it's fair to say that Splitpush strategies can counter him a bit too, because as Karthus you want that huge 5on5 figt, where you can AOE-damage the whole enemy team. However his waveclearing is phenomenal and with teleport up, he can end a splitpush pretty fast.

Thanks for reading and have fun with Karthus. Feel free to comment or suggest stuff. If you liked it consider to upvote it as well. I apologize for any grammar mistakes, my mother tongue is German, not English.

2013/03/01 - Guide created