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Karthus Build Guide by crystalfortress

AP Carry AP Mid Karthus - So Many Souls Await!

AP Carry AP Mid Karthus - So Many Souls Await!

Updated on September 4, 2014
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League of Legends Build Guide Author crystalfortress Build Guide By crystalfortress 4 2 58,706 Views 15 Comments
4 2 58,706 Views 15 Comments League of Legends Build Guide Author crystalfortress Karthus Build Guide By crystalfortress Updated on September 4, 2014
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Hi there, my name's Crystalfortress, and this is my guide to AP Mid Lane Karthus, as well as my fourth guide on Mobafire. The recent visual update of Karthus has caused me to notice him again, and when I went to mobafire, I was disappointed with the selection of guides on this awesomely fun to play champion, so I decided to make my own. Make sure to vote on how you feel about the guide, and give me any tips that you can think of in the comments section. I will make sure to check them often and will reply to you and listen to any suggestions or complaints.
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  • Incredible late game
  • Safe laning phase
  • Global damage ultimate
  • 7 assured seconds of damage
  • Squishy, especially early game
  • No hard CC
  • Proper Ult use requires communication
  • Mana hungry for pushing or aggression
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The offense tree is extremely important for any kind of AP or AD carry, as it gives some sizable bonuses to the damage that they will be focusing on dealing. The route I take through the tree is fairly regular, other than the point in Expose Weakness instead of Arcane Blade , which I take on Karthus because you don't use your autoattack for anything, even farming (unlike most champs), so that point would be useless. However, if you would rather have the sustain from Feast than the additional damage from every member of your team from Expose Weakness (including yourself, I might add), then that is a perfectly viable option, which I sometimes use myself.


The utility tree is great for AP Casters, as the Mana regeneration can really help early game, the summoner spell cooldown reduction is helpful, but most of all, the buff duration is really helpful for relying better on blue buff.


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Ability Power to deal more damage. Fairly simple choice.


Currently the best defensive seals in my opinion, as armor seals were nerfed. Scaling because they surpass their flat alternatives around level 6, and your safe laning phase doesn't require the early health.


Magic resist is useful against AP mid laners, who are the norm these days. They'll protect you against a lot of their damage so you can stay in lane longer.


These marks are by far the best for AP mid laners. They provide more damage and stay relevant throughout the game better than any other mark. Not hybrid because you don't harass or farm with your autoattacks.



These are what I'm currently using on all of my rune pages, but that's just because I haven't bought any other quintessences yet. They work fine on all champions.


I would consider running these against an AD mid laner like Zed or Yasuo. I currently use these instead of scaling health because I don't have enough rune pages, so the ones that i do have need to be widely applicable.


These could be used instead of magic resist in the situation where you won't be needing the extra magic damage defense, whether because you counter your lane opponent or because you are against an AD mid laner.
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Flash is an absolute necessity on Karthus, as it is with most mid laners. Karthus has absolutely no mobility built in to his kit, so you rely on this to get you out of sticky situations or in to teamfights. Irreplacable on Karthus in my opinion.

Exhaust is really good on Karthus. First off, you have almost no crowd control in your regular kit, with the exception of Wall of Pain, and that's one thing this provides. Also, one of your main weaknesses is enemies that can all-in you because of how squishy you are. By cutting their damage in half, this summoner spell decreases the likelihood of them finishing you off, and if they do, they're stuck in your 7-second damage zone while heavily slowed.


Teleport can be helpful against an enemy that will definitely push you out of lane, as it can allow you to recall back to base, buy, heal up, and then immediately Teleport back to your turret (which now decreases the cooldown). It can also be nice in an especially bad matchup by allowing you to make global plays, and hopefully get other lanes rolling since you'll have trouble doing it in your own lane.
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This is the way that I would probably level my abilities against most laners. You obviously want to start with Lay Waste, because it is how you farm. The passive from Defile is extremely important for mana sustain while farming with Lay Waste, so it has to come second. Here, you can choose to either put a point into Wall of Pain, or put another point into Lay Waste then a point into Wall of Pain at level 4, or you can even wait longer than that if the enemy laner and jungler are both very passive early game. You have to make this decision depending upon two things: Whether you need the slow from Wall of Pain to stop the enemy mid laner's aggression, and also if you are having a hard time farming with level 1 Lay Waste. After that, max Lay Waste for ease of farming and also possibly harassing the enemy laner, then Defile for area of effect damage, and finally Wall of Pain, taking points in Requiem at 6, 11, and 16.



Death Defied is one of the parts of Karthus that really defines him as a character. It makes it so that, instead of immediately dying when you take lethal damage, you enter a spirit state, in which you can still cast spells (free of mana charge) but cannot move. This makes it so that, when you die, your corpse becomes a humongous, scary damage zone for your enemies to either avoid or face your wrath. It also makes it easy to punish enemies overcommiting to kill you, especially if they are close range champions, because they will end up in the middle of a large damage zone once they finish you. One big thing to keep in mind is that you can still cast Requiem from the grave, so it is often best to save it for the very end of a team fight to secure kills instead of early on, as not only will you definitely have the necessary channel time after death, but it also cannot be interrupted this way.


Lay Waste is an extremely important spell for Karthus. It is an extremely low cooldown, very small area of effect, delayed damage spell. A few things to keep in mind with this spell are: 1. The delay is 0.5 seconds, 2. the damage is doubled if it only hits one enemy, 3. The mana cost is low enough that if you last hit your enemy with it, the passive from Defile will almost entirely refund the mana cost 4. This spell is autocasted, whether you have it set that way or not. One of the main uses of this spell is as a way to farm minions (there are tips for this in the TIPS AND TRICKS chapter). However, you can also use it quite effectively to zone or harass enemies, especially close range ones, by placing it between them and the minions they may be trying to farm. It is also has insane damage output in teamfights or skirmishes. If you can, try to hit the carries with it such that it hits no one else, as one of them can practically take half their health in the late game. However, it is fairly easy to dodge, so don't be too hard on yourself if you miss an enemy champion.

This spell is a one-point wonder. It creates a wall centered at the targetted location, with the wall itself extending equally to the right and left at an angle perpendicular to Karthus. Any enemies that pass through the wall are slowed and have their magic resist reduced by a percentage. Since this ability deals no damage, it has the least priority in terms of leveling. However, as Karthus' only source of crowd control (unless you take Rylai's Crystal Scepter), it is actually an extremely important part of your kit, allowing you to keep up with enemies fleeing from you or keep enemies away that you are trying to flee from. The magic resistance reduction also is a really nice form of damage amplification that also synergizes nicely with any magic damage the rest of your team deals.

Defile is one of the main ways that you deal damage in teamfights, as well as a great spell for pushing the lane. It is a toggle ability, meaning that activating it turns it on or off instead of creating a singular effect, and also that it has only a short cooldown between toggling. When it is turned on, it creates a large area around Karthus in which enemies take a large amount of damage per second. However, this ability comsumes an insane amount of mana while it is toggled on, so don't leave it on! When it is toggled off, Karthus recieves a large amount of mana every time that he kills an enemy. This passive is extremely important, as you should be doing almost all of your farming with Lay Waste, and that can get expensive. Level this second for the mana sustain, and max it second for the damage over time while toggled on.


One of the most awesome and feared ultimates in the game. When you press R, Karthus channels for 4 seconds. When the channel finishes, all enemy champions, no matter where they are and whether or not you have visibility of them, take a large amount of damage. Use it in the early game to finish off low health enemies anywhere on the map. During teamfights, be sure to save it for the end of the teamfight, as there will often be low-health stragglers, and using it at the beginning of a fight is silly, as they will often just run and let you waste a cooldown. Death Defied makes it fine to even wait until you are dead. However, keep in mind that you can't start the channel after 3 seconds of Death Defied, so don't wait too late.
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The Doran's Ring start is a really good start, as it provides you with a whole lot of mana sustain, a really important thing for Karthus since you do all of your farming with Lay Waste. It also provides you with some really nice starting stats in health and ability power for early game aggression and ease of farming with Lay Waste, as well as a couple of Health Potions, which are mostly unnecessary due to Karthus' safe laning phase. A solid start, providing you with a huge amount of health sustain and a little bit of mana sustain (you don't really need that much if you are playing safe, since a lot comes from Defile's passive). However, this amount of health sustain is rarely necessary since you have a pretty safe early game, and can safely farm with Lay Waste out of the range of most enemy mid laners. A niche start on Karthus, but still a possibility.


catalyst the protector
catalyst the protector is important for building into Rod of Ages, an extremely important early item for Karthus. The stats it provides on its own are also quite nice, as well as the passive that provides you with quite a lot of both health and mana sustain in the early game. Most importantly though, builds into Rod of Ages.

The second ingredient in Rod of Ages. The statistical advantage it provides is quite clear, with ability power being your main damage stat. However, if I had to choose between building one of these early or a catalyst the protector, I would choose the catalyst, as it provides you with more helpful laning stats, since you mainly just want to farm in the early game and damage isn't important for farming. Boots are a good early game item to pick up on almost any champion. They are especially good on Karthus due to his low mobility. They can allow you to flee from a bad situation or catch up to a fleeing enemy, as well as dodge skillshots better.

if you can afford one, picking up an early Needlessly Large Rod can make your damage skyrocket above the enemy laner's. It's especially good if you are against an AD mid laner, since you will want to be building an early Zhonya's Hourglass, and this is an ingredient. However, it is good to build against any enemy, as you will eventually be building a Rabadon's Deathcap. A very good item to build early game if you are against an AD mid laner, as it provides you with a good amount of armor to help mitigate their physical damage. It also builds into Zhonya's Hourglass, an extremely important item against AD mid laners, and good in any matchup. The item itself doesn't provide a lot of AP for the price, but the armor is important to get. This can be a good item to build if you are against an AP mid laner that is giving you a lot of trouble in lane. It also builds into Abyssal Mask, a very good item against AP mid laners. Doesn't provide you with any offensive stats, so I wouldn't suggest building it until after Rod of Ages is complete, unless you are getting forced out of lane by A LOT of magic damage.


These are your three core offensive items, so against an AP mid opponent, it's best to rush them. You'll be doing pretty humongous damage, have lots of mana, and nice defensive stats in health and a nice shield active from Archangel's Staff. Important items to rush agaisnt AD opponents. Virtually the same as the set against AP opponents, but instead of finishing seraph's embrace, you start to build into Zhonya's Hourglass early, as you will more than likely need the early armor.


The boots that you will almost always get. Simply the best tier 2 boot choice in most situations, because you don't need the added mobility of Mobility Boots or Boots of Swiftness, and provides the best stats for magic damage mid laners. Magic penetration is a really good stat that multiplies your damage by cutting through the enemy's magic resist.

An extremely important item for Karthus. He needs mana for agression, as a matter of fact, anything other than farming. He's also extremely squishy in the early game without any tankiness, and the 600 health is helpful for that. It also provides a pretty good amount of ability power. The sustain passive is also extremely helpful, unfortunately only until level 18. Be sure to get it early to stack it up quickly.

Seraph's Embrace is an awesome item on Karthus. In combination with Rod of Ages, it will provide you with all of the mana that you will ever need. It also provides a lot of ability power, mostly through the passive. The active component is really nice for Karthus, giving you a humongous shield that can give you more time alive when diving into the middle of an enemy team.

A great item on Karthus. It will provide you with some really nice armor. It also provides you with 120 ability power, which is quite a lot. However, one of the biggest selling points of this item is the active. When activated, it makes you temporarily invulnerable and untargettable, but also unable to move. Since you can still have your Defile on while this is going, this is pretty basically 2.5 seconds of free damage.

Rabadon's Deathcap provides a huge amount of ability power, more than any other item. It is pretty basically necessary on almost all ability power carries. It provides a huge ability power boost, especially in combination with other ability power items due to the percent increase passive.

Void Staff is a really good item late game. The percent magic penetration is incredibly helpful for damage in general, but especially against tanks, who often build a lot of magic resistance. It also provides you with 70 ability power, a solid amount. In addition to Abyssal Mask, this is one of the few items in the core build that I would consider replacing.


This item could be a good replacement for Rod of Ages. The main difference between Rod of Ages that makes Rod of Ages more core is that this doesn't provide any mana, which is a pretty good stat on karthus to keep Defile going on for as long as possible and has great synergy with Seraph's Embrace. However, this item provides you with a passive that gives you a slow. Originally unbeknownst to me, the %35 slow can be applied by a single-target Lay Waste. Using this can give you incredible catch potential because they will be literally constantly slowed and it will be super easy to hit them with follow-up Lay Wastes. Thanks to WalterBurn for pointing this out.

I often take this item instead of Void Staff. It provides similar stats, but instead of %magic penetration, it gives 20 magic resist reduction in an aura around Karthus, as well as some magic resist. The main reasons that I would take this instead of Void Staff was if their team was dealing a lot of magic damage to me or if my team had lots of magic damage, because then the aura of magic resist reduction would help them too. Otherwise, stick with Void Staff.

Mercury's Treads could be used instead of Sorcerer's Shoes in the situation where the enemy team has some sort of really scary crowd control. However, I would probably not suggest taking both this and Cleanse. The tenacity is really helpful for escaping from bad situations when you get hit by that scary crowd control. The magic resistance is also helpful, but the major attraction is the tenacity.

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Playing as Karthus in the early game, you usually want to play extremely passively. Use Lay Waste to farm minions from really far away and occasionally harass the enemy laner if you get the chance. If you can, try to keep the lane from pushing towards you, as you can't farm under turret that easily (more easily than a lot of champions, honestly, but it's still not easy). However, at the same time, try not to push the wave yourself, as you have very little chance of escaping from a gank if your enemy knows what they're doing, due to your lack of crowd control and mobility. If your jungler ganks, try to hit the enemy with Wall of Pain and hope your jungler has some crowd control themselves, otherwise you almost certainly won't get the kill. Announce to your team when you hit level 6, and they may call on you to ult to secure kills that are getting away. You pretty basically never have to roam at all, because you can rely on Requiem for your global pressure. Just make sure to focus on farm, farm, farm.


Usually, your strategy throughout the mid game is very similar to the early game: farm, farm, farm. You want to make sure to have as much of a gold advantage as you can by the late game, which is when you start to really have an impact on the game. Make sure to continue using Requiem to secure fleeing kills around the map and apply global pressure. The only reason you should stop farming your lane is to help an ally in a nearby skirmish in the jungle. If your team wants to do dragon, usually because they got the bottom lane turret or some kills, that is the only other time that you should leave lane.


Now is when Karthus really starts to shine. So long as you've properly farmed your lane, you should be dealing pretty humongous amounts of damage. During teamfights, get as far in as possible with Defile active, and watch the health bars drop whilst spamming Lay Waste, preferably all over the carries. Use Requiem to finish off any stragglers. It may seem scary jumping right into the middle of the enemy team as a somewhat squishy mid laner, but you have a few things going your way. First of all, so long as your tank isn't an idiot, he should be trying to keep the enemy damage dealers off of you for as long as possible. In addition, you can rely on Zhonya's Hourglass and Death Defied to get you a good amount of time in the middle of the enemy team no matter what. You can also easily kite close range opponents using Wall of Pain, just watch it's fairly long cooldown. During sieges, try to poke or zone your enemies using Lay Waste and possibly Wall of Pain.
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Tips & Tricks

  • A lot of enemies forget about Death Defied and stick around in Karthus' damage zone after they've killed him. Try to take advange of this by making sure to die in the right spot in a teamfight.
  • Single-target Lay Waste does an exceptional amount of damage, especially considering it only has a 1 second cooldown. When harassing or dueling with an enemy, try to hit only them with it.
  • Karthus farms in a pretty unique way. What you want to do is never use your autoattack to farm, and instead rely on Lay Waste. It has a low enough cooldown and mana cost that you can use it constantly for this purpose. It is often easier to last hit an enemy minion with Lay Waste if you hit it with the single-target damage. This takes some getting used to, especially if it is near other minions, but the recent visual update has given Lay Waste a visual circle showing the area of effect on cast. Take a while to get accustomed to the area of effect, and it quickly becomes easy. You can also quickly toggle Defile on then off to secure a CS if your Lay Waste is on cooldown.
  • In solo queue, it can often be hard for allies to communicate that someone is getting away low enough that Requiem would secure the kill. I would suggest giving them some sort of code word to quickly type in chat in this event. Something quick and simple that you can easily remember. I like to use a simple "kr" myself, which I remember because it stands for Karthus R.
  • One highly underrated part of Lay Waste is the small vision bubble that it grants when cast. You can use it to check bushes from very far away, since most enemies lurk near the corners when looking for a jump on someone. Wall of Pain also gives vision, but it has a long cooldown and is your only form of crowd control, so I probably wouldn't use it for that.
  • Enemies that can temporarily become untargettable or invincible can use this to avoid the damage from Requiem. However, if you see them using these abilities to get out of sticky situations, try to remember their cooldowns and see if you can't take advantage of the ability's downtime.
  • Don't forget to turn off Defile when you are not using it. It uses huge amounts of mana.
  • The new dance (ctrl+3) after the visual update makes a really annoying noise. Spam it, and your enemy may just rage quit. (just kidding, don't be that guy)
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Synergies / Counters


Karthus has a few things that he synergizes really well with. First of all, area of effect crowd control can allow him to get off a lot of damage with Defile and Lay Waste without the enemy having any option to retreat ( Amumu, Varus). Secondly, allies that also have global or extreme-range spells can be used in tandem with Requiem to create huge global pressure, which the enemy team has to react to by either playing passively or being ready to fight with numbers against them ( Pantheon, Nocturne). In addition, any allies that can help protect you when you dive into teamfights will allow you to do the most possible damage ( Kayle, Yorick).


Karthus has a few things that counter him really well. First of all, any enemy that can become temporarily untargettable or invincible has the capability to avoid Requiem's damage ( Fizz, Kayle). Secondly, while he may have the capability to farm at a longer range than almost any other mid laner, enemies with extremely long range harass can punish him for his lack of health sustain and force him to miss some of the farm that he needs so badly ( Zed, Lux). The last thing that really hurts him is high mobility and burst, which allows them to quickly jump on you and kill you due to your lack of crowd control and mobility and then get out of your corpse's damage zone ( Kassadin, Akali)
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Thank you very much for reading my guide! I hope that you enjoyed it and that it helped you learn how to play or become better with Karthus. If you did enjoy the guide, I would really appreciate it if you would take the time to upvote the guide, as that would allow it to get more publicity and hopefully help out more people! In addition, if you notice anything that you don't agree with or would like to have a discussion about the guide, make sure to drop me a comment! I will make sure to check them and reply! Anyways, thanks again and hope you enjoyed the guide!
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6/6/2014: Guide published.
6/7/2014: Moved Seraph's Embrace to core items and Abyssal Mask to situational, as well as removing a bunch of situationals.
8/8/2014: Changed Exhaust to the main summoner spell other than Flash. Changed some portions of text to fit accordingly, and added some tips to the spell leveling order explanation section and masteries section by the advice of Janitsu.
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League of Legends Build Guide Author crystalfortress
crystalfortress Karthus Guide
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AP Mid Karthus - So Many Souls Await!

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