Hello everyone! In this guide I will show you how I prefer to play Karthus: The Deathsinger aka the Lich and better known as the Grim Reaper. Why? Because karthus is a master at killing champions and his Grim Reaper skin is bad ***! The objective in my build is to minimize the inherent weaknesses Karthus has while at the same time maximizing his strengths. Normally i take the middle lane as karthus or the solo lane if we have a jungler. However, it is not absolutely necessary to be mid and can still rack up many kills without going mid but it does help tremendously because you want requiem as soon as possible. This guide I hope will be beneficial for those starting out with Karthus and give insight and techniques to those who are more advanced with him. I have played Karthus for a while now and want to share what i have learned playing him. In my past games my best k/d ratio with karth was 38/0 as a ratio. However my personal record in just the amount of kills was 56 kills in one game. I don't know why to this day they didn't surrender but oh well. I personally think karthus is a great champion and very fun to play. If you have questions, comments, concerns, feel free to post or add me k hill093. I hope you enjoy the guide!

Pros

-Massive dmg capabilites
-Great AoE and a wall that can also slow multiple enemites
-Amazing mid champion
-Good Harasser
-Good Farmer
-He has a sick passive
Karth's ulti can be very effective in getting kills and changing the flow of a team fight.

Cons

-He's very squishy
-Needs a good amount of kills to be effective late game
-Tends to be focused in team fights
-Very item dependent to be effective with abilities especially his ulti
-Items/Abilities that can counter Karth's ult
-Defile can drain mana early if not careful

I think masteries are of personal preference but i personally think 9/0/21 is the best for karth for the following reasons:

Utility:
-health regan
-reduced cd of teleport
-level quicker
-expanded mana pool
-increased move speed
-cool down reduction for ulti and wall
-reduced cool down time of summoner abilities which i find useful for karth

Offense:
-AP per level
-CD reduction
-Magic Pen

x9 Greater Marks of Insight

Magic Pen is very important to karthus especially early when you don't have hundreds and hundreds of ability power to fuel your damage. Magic Pen is good for lowering defenses allowing for greater success with ulti and other spells


x7 Greater Seals of Potency
Speaking of ability power to fuel your damage. Karthus needs AP even in early game because Karthus has to be able to pick up a kill relatively quickly to be effective in the later phases of the game.
Greater Seal of Vitality
x2 Greater Seals of Vitality
I personally like at least some extra health on karthus. He is a very squishy champ and i find the last two seals of potency that would have made 1.18 not as valuable as an extra boost to health personally. But if in personal preference u feel you'd rather have the extra 1.18 ap then finish getting Greater Seals of Potency in place of vitality.


x7
Same reasoning as the Greater Seals of Potency more ap= more dmg=more kills


x2 Greater Glyph of Force
This one I have to explain a little. Although Karthus does need early AP, AP over time helps while being in lane to continue being effective and threatening without so many trips to base to shop for items missing out on exp.


x2 Greater Quintessence of Potency
Again more ap = more rape. AP AP AP>>>>>Cooldown reduction for karth why? all of his damaging spells except his ulti have very short cool downs.


x1
One Quintessence of Force gives a good boost to your AP over time and allows your enemies to feel the weight of your spells and not stagnate in output of your damage.

Summoner Abilites i find also to be a matter of personal preference. However this said i find heal and teleport to be the best options for karthus.

My Summoner Abilities

You might be wondering why of all the summoner abilities i consider heal to be the best option next to teleport for karthus. I get heal for the following key reasons..
-By getting heal you minimize karthus' most prominent weakness..SQUISHINESS!
-With heal you can deceive enemies in how much health you really have and can pick up kills with it and gives great early kill capabilities
- You can use it to tower dive go in get your kill and heal on the way out. only if experienced with karth do i recommend it.
- You can save teammates in certain situations
- You can stay in lane longer

Teleport is an amazing summoner ability. Not only does it let you travel places quickly which is the last way i use teleport it has many, many uses..
-You can use teleport as a ganking tool by teleporting on a minion, or a ward including a teemo shroom when enemy near it put up wall behind them move in with defile and lay waste and you have a very good chance for a kill if not a double kill.
-If for some reason your team engages in a team fight and your not there you can use teleport to get to the action to help. Karth is a heavy asset in a team fight
- You can use teleport as a quick escape. If for instance an enemy catches u in a jungle. Put up a wall and u can find a safe zone to tele combined with heal can get you out of a bad spot.
-If you do need to recall early Lets say your clinging to 20hp. Teleport is good to travel back to your lane after recalling not because of laziness but because karth needs all the exp he can and the quicker u get back the better.

Other Good Summoner Abilities for Karthus

Ghost is good for moving with defile being able to catch up with fleeing enemies. I don't think it is as good as teleport which u can use to cut off enemies fleeing in a lane and you have a Wall that has a long slow to catch people and if they really that low on hp just ulti your a karth after all ;)
ignite can be used to lower an enemy to the point you can ulti them. Usually i don't take this because i don't think ignite is as good especially since you have great harassment abilities already and it doesn't give as much survivability as heal
Flash provides a good escape ability which karthus does lack besides his wall. Keep in mind that your defile is much weaker than fiddle's ult and u cant just flash and auto kill with defile. Flash can be good with different scenarios but doesn't give as much early opportunity for kills as heal and teleport.
Clairvoyance is a good summoner ability for those starting out with karthus. It can be used as a way to make sure you won't get ganked which gives it a survivability aspect and if you are starting out with karth and your looking around checking on other lanes and didn't quite catch the retreating enemies health clairvoyance gives you that second look that you might need. I personally don't take clairvoyance because after experience with karthus you don't need that second look as much and your judgment on when to ulti will improve with practice and time.
Clairty is also good for those starting out with karth and even experienced karth players that are very good take it including a buddy of mine Antic101 was inspired by me to play karth takes clarity and does very well . Clarity gives you a larger mana pool which means more time you can defile and you'll never have to worry about being oom for an ulti. I personally don't take clarity because i feel that i can manage my mana fine without it and rarely do i run into a situation where i don't have enough mana to ulti. Also being able to recall and teleport also provides the same benefits clarity would while laning and teleport can be used more viably in more situations. There is a trick with requiem i will share later in the guide so that clarity is not needed as much.
Exhaust can viable in certain situations especially since how squishy Karthus is Exhaust can provide a way of dealing with and even killing melee champs trying to gank you, as well as a way of escaping while your wall is on cool down.
I can see this ability being useful although personally i have never used it. It could be a means of escaping to get room to ulti or chase down champs that slowed you and now fleeing in terror

WHAT NOT TO GET

Revive: Stupid...Who even gets this ability anyways?
Rally: Your not an AD champ you don't pick rally
Fortify: Not necessary for karth at all and has no practical use for karth

Passive:Death Defied

Death Defied is a great passive. This passive gives karthus a 20% quicker timer to re-spawn after death which is very nice because seriously who likes waiting that much time to re-spawn? No one that's who..
The second more important effect of karthus' passive is that he can continue to cast for 8seconds meaning you have a shot of redemption! You can wreak havoc on the enemy team and they cant do anything but take it or move out of the way which is very hard to do in a team fight. Best of all your dead meaning your skills cost 0 mana so spam everything you can and do as much as possible damage until it wears off. Used effectively this passive can turn the tide of a team fight and give your teammates a real advantage. Although there is debate that karthus' passive should be something to help prevent dying than having an effect after the fact. Funny that one of karths' greatest assets can only be maximized by dying. I utilize his ulti in a technique i developed and maybe others do it too called : Kamikaze "see the strategies, tricks, and technique's section"

Lay Waste

Lay waste is your primary harassing/farming tool. The placing and accuracy of using lay waste separates the great karthus' from the average. Try if you can to use it so you benefit from the double damage bonus for hitting a single target. When enemies are running toward you is a good time. You can use lay waste defensively as well nothing makes someone think twice about chasing you than bombs under their feet. With rylai's you can kite with this ability as well.

Wall of Pain

Placing your Wall of Pain is crucial to set your self up for kills/ganks and also to defend yourself and run away and save yourself from a gank which your teammates so conveniently forgot to call mia -.- This is a 7 second slow in other words they are slowed for a pretty long time and you have time to catch them if u need to if they are hit by your wall. This skill works well with teleport in setting up ganks from teleport. In additon to slowing many forget that the wall reduces magic pen and armor meaning you and your team can do more damage to them when enemies pass through your wall and does have a role to play in team fights. This wall is not like anivia's meaning your team can pass through it and nothing will happen to them.

Defile

Passive: Defile is a great tool to help you stay in your lane and farming. It allows you to restore you mana and while laning and keep you in the field longer so you don't have to go back to base so often because of mana issues
Active: Do not leave your defile on by accident! This ability drains your mana and the longer you have it out it will take more of your mana. This ability is great for when enemies are chasing you think twice with an aura up that ticks for whenever they are near you. This ability is great in team fights affecting all enemy champions allowing karthus to damage multiple enemies at the same time.

REQUIEM!!!

Okay this ult is one of the more controversial ultis in League of Legends. It allows karthus after three seconds of channeling to hit every champion on the map guaranteed. Getting kills with this ulti will make many many people upset with you. What people don't know is karth's ult is one of the longest CDs for an ult in the game and doesn't do that much damage compared to other champions' ulties comparatively.

Uses for Karth's Ult:
- As Karthus you have the job of preventing escape of low hp champs you can use your ulti to score a easy kill even sometimes a double or triple kill to get you fed early and quickly as possible because late game isn't very kind to karthus without the early kills. Once fed your requiems will start doing more and more damage and be very effective in killing enemy champions.
-If you see a situation where the enemies and your teammates are engaged in a fight and the fight could go either way. It is OK to get assists from his ulti especially with a mejal's soulstealer you can even build AP from it. Don't be overly greedy you can save your team and turn the tide of a fight with your ulti when used properly.
-Team fights: There are two options when to ulti when in a full on team fight.. when your team engages the other team and you both start going at it and escape is unlikely an ulti then can win a team fight by the dmg u would cause allowing your team to push.
The other option is towards the end or at the end of a team fight to finish them off u can ulti then.
-There are soo many ways of using karths ulti people don't think of right way you can use it to save teammates scaring off enemy champions chasing them.
Note: If you are ulting and you constantly not killing them by like 30hp or some stupid number stop to consider if you are factoring in their magic resistance when you ulti. In other words even though it says the ult does 250 they might have 40 magic resist making your base 210. So the damage you will hit them for is: 250- their MR + your MP + your AP bonus. Also consider champions that can negate and counter your ult. Keep in mind all champions that have a shield a sanguine pool a heal and a banshees vale, hex drinker, or zhonya's hourglass. Also it is nice that your teammates want to help you call ultis but you have no right to get pissed if you trust them and u don't get the kill. They might not be considering all the factors that go into it like i am telling you. As karthus it is your responsibility to keep your eyes peeled for opportunities to use your ulti and use it best to help your team win. This is why karth isn't a noob champ you are responsible for dealing with the enemies in your lane + keep track of other lanes and whats happening to make your self as effective as possible. Also note that requiem should NOT be your primary killer compared the combination of karthus' three previous moves and i credit the combination of lay waste, Wall of Pain, and Defile more kills than i do requiem. Requiem has a 180 second cool down 1st rank without any cd reduction from masteries or runes. Meaning if you can only maybe get a kill once every 180seconds (120seconds max rank) keeping in mind there is a possibility you won't get the kill your talking one kill per 6minutes with your ulti assuming you get the kill on the second attempt. This is why i don't consider karth's ulti cheap or a noob ulti or an noob skill because so many things can go wrong that can prevent you from getting the requiem kill if you don't know how and when and how to use it and a long wait time before the opportunity to ulti again.

In this section i will be going over how to build Karthus and will walk you through reasoning behind selections i pick.
Best starting item for karth imo. Solves many squishiness issues right then and there. Gives Mana regen which is great for staying in lane and also gives you a nice bonus of an extra 15 AP. Following the guide as far as rune choice and masteries you should be starting games with doran's ring with about 37 Ability Power.

On your first trip back get amplifying tome and a boots of speed . This gives much needed quickness and a nice early boost to AP
During this time you'll be just about level 5 or 6. If you are doing well in other words have more kills than deaths get a Mejai's Soulstealerif not skip it and wait until you are doing better later. This item is pretty cheap and can get you massive amounts of AP allowing you to build up your mana pool.
Note: if you are even or have as many kills as deaths i would skip mejai's until you pick up a kill or two without dying then go back and get mejai's.

Next your objective is to expand your mana pool while simultaneously maintain a good ammount of Ability Power. We can do this by building towards an Archangel's Staff. Get a Sapphire Crystal . Next you will want more movement speed and magic pen to make your spells and ulti more effective so grab Sorcerer's Shoes. Next upgrade your sapphire's crystal to a Tear of the Goddess . This item solves any mana issues and as you mana pool expands you have the potential to do more damage by being able to cast more spells. Having a larger mana pool also allows you to hold out defile's aura for longer periods of time without worrying if you'll have enough mana to finish opponents with requiem. Afterward The next item is your blasting wand .
If you feel your lacking in AP by this point either you didn't get Mejai's or you decided to risk it and go for it and not doing so well all of a sudden i would buy an Elixir of Brilliance before i grind out the 1k gold for the Archangel's Staff. If you are doing well then an elixir isn't necessary and you can easily pick up kills to build your Archangel's Staff

After building your Archangel's you should be wondering hmm i'm kinda low on hp. This is why i build Rylai's Crystal Scepter next. Rylai's staff is great on karthus allowing defile and lay waste to have a slow component give's you a kiting/cc capability survivability and more ap. The first item I get building up to Rylai's Crystal Scepter is Giant's Belt. This belt gives a much needed 430 hp boost. After i get Giant's belt i tend to sell my doran's around this time. Once you have built your Rylai's Crystal Scepterthis item gives +500 hp 80+ AP and a slow on your lay wastes and defile which is great. You can use this slow to escape, chase, kite, and be the most feared champ on the field. After finishing rylai's you should be anywhere between 300-380 AP by this time depending on how your mejai's is coming along, 2k health and a good sized mana pool so you dont have to worry about going oom using defile as much. After you get your ryjal's you really want to hammer the opponent. This is the time where they start getting more hp more resistance and you want to shut the door on them. This is when you build your Rabadon's Deathcap!!! . Rabadon's Deathcap gives you 155 AP and amplifies your AP by 30%!!! Now that you have your items you should be causing serious havoc. But if for whatever reason you have one of those long drawn out games i have a couple suggestions for end game.

Note: If you feel you are lacking in AP after your archangels and you feel u really need the AP boost or a huge jump in AP earlier in the game for any reason, switching the order of rabadon's death cap and rylai's is a perfectly viable option. But i do feel in most cases the benefits rylai gives is more essential to get earlier than the ap boost rabadon gives. However, i do understand that there are games where that is not the case and the fact that some people might prefer to play with these two items switched.

Additions to build for end game

End Game building for karth i find is highly situational meaning you get based on what your team needs and what the other team is doing. By this time they might have figured out to get a Banshee's Vale. Sometimes you just need to stack AP and burn them other times you need to sacrifice some AP for survivability.

-Lich's Bane. This item is great for karthus end game. You can sell your boots if you choose since lich's bane can give you your move speed and your ryjal's can still slow people down. Lich's bane is amazing end game. 350mana 30 magic resist +7 movement speed and the unique effect is astounding. Just think auto attacks with your wand for 700+ per 2seconds. This gives karthus the ability to push towers quickly if no one on your team can seem to do the job and can bring down tanks and single targets quicker.
-If you sell boots for lich's bane you can choose a couple things you could go full AP keeping only your ryjal's for slowing deathcap and lich's bane and buying two additional Archangel's staffs. This gives karthus well over 1k ap but you have low survivability but massive damage.
Or after getting lich's bane you might want more defenses.

-Zhonya's HourglassThis is another great alternative especially fighting alot of melee or in general can do alot of damage to you such as viegar's ulti Gives armor, +100 AP and the stasis ability of the old Zhonya's Ring giving much needed survivability late game.

-Banshee's Vale if you need survivability and blocking a spell is necessary i.e living against an ulti from a viegar or any other nuke or ability that really other wise would decimate a squishy mage.

-Void Staff
Great item to get end game if you notice them stacking MR against you.

-Will of the Ancients
End game the spell vamp really does help and gives team a buff, more AP. Overall a good item to consider getting end game

Strategies

-As Karth you want to try as much as possible to get the middle lane or the solo lane if your team has someone jungling. If you don't it is still okay and i have done very well without getting middle or solo lane. The middle or solo lane still better to level up faster to get requiem quickly. You want to be the one ahead in levels as karth as much as possible makes it easier to get early kills.
-Ganking: Karthus is a masterful ganker with his wall combined with his defile and lay waste can make karthus a great ganker.
- Wall of Pain can be used to keep the enemy champs from engaging while your team is taking a tower or prevent champs from escaping while a tower is blasting them and lay waste to finish them(an easy way to score a kill)
-Don't be shy in using lay waste it has a very short cd but don't over spam either keep focused and really try to predict not where the enemy is but where the enemy will be is key to aiming lay waste.

Tricks/Techniques

- I discussed many tricks and techniques already in my guide but i will go over the ones i already mentioned to recap and add a couple:

-Tele Ganking/Tele into team fights: You can use teleport on a ward or friendly minion when enemies are close to go for an unexpected gank. Great for scoring early kills if used effectively. Teleporting into a team fight once both sides are engaged can devastate the other team by the element of surprise.

-Using heal as deception/baiting: when in a early 1v1 fight lets say with a teemo and it seems close like neck and neck but you have a heal wait till your health drops to about 35% pop heal and now you have the clear advantage and teemo can do nothing and you pick up the kill ( be careful with ignite reducing the benefit of heal)

- Double damage with lay waste: When harassing try if possible to catch enemy champs alone without hitting a creep you do double damage which is a great payoff for a very little amount of mana cost. You can also be deceptive with your double damage bonus with lay waste: for instance if your in a fight but teemo has minions around him so you use the same technique as before and use heal to deceive teemo but also activate defile to also do damage to minions. When you heal all of a sudden teemo is left with no minions to guard him and now your doing double damage with lay waste giving you the clear advantage and the kill.

-Kamikaze: This is my personal technique that i love. When you realize your not going to have a perfect game and you want to build yourself up and benefit the team and you have a good amount of ability power. A great thing you can do is die. I'm actually 100% serious. In a team fight let your team engage then you go in defile wall and lay waste as much as you can but make sure your not alone and actually with the team.. You will end up drawing attention by your damage and the enemies will more than likely focus you but keep doing as much damage as you can..Once dead wall keep defile up lay waste and above all else ULTI!! by this time the team fight would be winding down and ulting at this time can pick up at least a kill if not more and win the team fight with your noble sacrifice. Note: only do this once you feel comfortable with karth and you know you will end up doing more good than just feeding the team a kill. Another way to use kamikaze is when the enemies are about to take a tower you can teleport on the tower put up a wall defile and lay waste. You have a good shot of getting at least a kill or a double out even a triple of this but you will most likely die but maybe also save a tower. A kamikaze is a SACRIFICE not SUICIDE don't teleport into their entire team alone and expect to get a penta-kill.
-For tips on requiem see the skills section of the guide for full explanation of how to work karth's ulti.

-Finally the last trick i have to share is if for whatever reason you do not have enough mana to ulti. You can still get the kill. How? Beat them to the recall! Let's say for whatever reason you went oom and for the most part direct fighting is over you couldn't kill them they couldn't kill you. But odds are they will take some time to make sure they are in a safe place to recall like a tower or in the jungle somewhere. What you can do is recall yourself before they get a chance too. Let's put in some numbers... Lets say it take you 8 seconds to recall and it takes them also the same amount of time as you to recall. Assuming it takes 1 second to get your mana from base and a 3 second channel for requiem. 8+1+3=11 seconds total but like i said both of you plan to recall so you have a 4 second window to recall before they do. So if it takes them 5 seconds before they can safely recall or not recall at all because they think they are safe at the tower or whatever. You have a chance of still scoring a kill with requiem. Note: the success rate is subjective to a great deal of factors and is much less than if you had mana, but i have gotten kills this way. Normally i use this trick most often before i start expanding my mana pool with AA but still high enough lvl to requiem. This trick is also good for finishing off your opponent that your facing in mid. Lets say you get away from a fight with 100 hp but your opponent has 175 hp and you don't have enough mana to ulti. Recall and finish him with Requiem!

So that's karthus.. I hope you enjoyed my guide and it helps you. Again i do have alot of experience playing karthus and have gotten many quadra couple penta kills as karthus and this build is the one i use and have developed myself from playing him and knowing how he works. People will say some funny comments when you are doing well and about how your ult is so easy. Just say back "According to riot Karth is listed as a hard champ". It's funny though i've fought many karths before also and i have seen alot of karths played incorrectly and no one seems to complain to the bad karths that his ulti is cheap. I hope you enjoyed it and feel free to post questions, comments, concerns and i will be more than happy to clarify and if i made a mistake or i missed something i'll definitely won't hesitate to update it. I probably will add more end game items and alternate ways of building for different situations. Please keep trolling to a minimum but other than that let me know what you think. I really do love karthus and happy to show people how much fun of champ he can be. I hope you enjoyed the guide and please don't down vote the guide unless you've tried it and didn't like it for whatever reason. But overall i think this build gives karthus a good sized mana pool, and ryjai for survivability and an enormous amount of AP to devastate your enemies making you be able to become death himself: The Grim Reaper!