[/b]Welcome one and all the the greatest Karthus builds ever! One is guaranteed to get you over 1000 AP or your money back! And the other is based on survivability as well as AP. These 2 builds give you a nice idea on how to build Karthus either straight AP damage or AP with survivability.

Pros :D
- Amazing early game harassment
- Creep farming is so easy
- Global Ult
- Passive is great
- Rage Quit Master

Cons D:
- Super squishy
- Always focused in team fights
- The item , among others, can counter your ultimate every 45 seconds.
- Everyone rages on him

The magic pen makes Karthus a force to be reckoned with and also help with dropping tanks early.
I used the flat AP for early game harassment,just to get that little edge on my prey.
Gets you more AP than flat runes after level 5, so these babies are a must. Give you a nice bit of AP late game.
Massive AP boost as you level yourself up. Same as the Glyphs, used for late game.

I use the standard 9/0/21. Notice I don't put any points in . Thats because Karthus' passive already takes away 20% of your time spent dead, so its not really needed.

I use so I can spam skills and no have to worry about mana. is for running to and from team fights and also used for escaping ganks.

Other options that would be suitable for Karthus include for getting back to lane or helping push other lanes. for getting away from ganks or , just cause it's heal.

Spells you should never need include , because you have to pick off low health champs. isn't needed because you have .

Passive- Upon dying, Karthus enters a spirit form allowing him to continue casting spells for 7 seconds. During this time his abilities cost no mana.

This allows you do be in the fight even after your dead. You can spam your skills and not have to worry about mana. It's great for team fights, when you died spam everything for a few seconds, than cast your ult as a final blow to help your team clutch the fight. It's also nice for when your in mid and your opponent decided to dive you, even if they kill you, they should have low enough hp for you to get the kill anyways.

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This is your Q skill- This is a AOE skill shot based skill, that can either deal damage to multiple enemies, or bonus damage to one.

This is the skill your opponent in mid will learn to hate you for. It deals 40 / 60 / 80 / 100 / 120 (+30% of ability power) to the enemies inside the blast zone, and if used on a single target, deals double damage. It only cost 20 / 26 / 32 / 38 / 44 mana, and combined with the passive from your using eben less mana if you can time it right. The best part of this skill is the cooldown tho. It's just 1 second! Which means its one of the highest damaging Q's in the game! Oh did I forget to mention that this skill, if used in a bush, will reveal a small part of it, letting you see enemies that might just be waiting to kill you. And with a range of 875 PLUS the AOE blast of 200, your looking at a 975 range poke that hurts so bad, the enemy won't come near you.

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This is your W skill- Creates a 800 / 900 / 1000 / 1100 / 1200 distance wide wall through target point.

This is a key skill for getting kills early game in the laning phase. After casted, the wall lasts for 7 seconds, which is nice because even if you miss your target, odds are there's a minion wave coming that will get hit instead. It drops your enemies armor AND MR by 15 / 20 / 25 / 30 / 35 and also slows them by up to 40 / 50 / 60 / 70 / 80% for 5 seconds. The movement speed debuff decreases over time. The wall costs 100 mana and should be used wisely. The wall is useful for so many things. Such as ganking, whats better than a 7 second wall that reduces all defensive stats, making it a for sure kill for you or your team. It can also act as a ward because it reveals enemies in bushes and the fog of war.

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This is your E spell. It's passive restores mana per kill on an enemy champion, minion, or neutral creature. When activated it drains mana to deal magic damage to nearby enemies each second.

This skill if very useful in keeping Karthus in lane. If you can time your Qs and auto attacks for last hitting, you will never run out of mana. It returns 20 / 27 / 34 / 41 / 48 per kill, and when activated drains 30 / 42 / 54 / 66 / 78 mana per second and deals 30 / 50 / 70 / 90 / 110 (+0.25 per ability power) damage per second. The AOE is 550, so it has a nice size to it. Late game this skill can be used to quickly farm minion waves. This skill shines in team fights, due to the large AOE it will deal a great ton of damage and combined with Zhonya's Hourglass it makes for even more damage.

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This is your R spell. After channeling for 3 seconds, Karthus deals magic damage to all enemy champions.

This is your ult and by far one of the most hated ults in the game. It deals 250 / 400 / 550 (+0.6 per ability power), costs 150 / 175 / 200 mana and has a cd of 180 / 150 / 120 seconds. Check the chapter Proper Use of Requiem for more details.

You want to level up as fast as you can so you can farm and harass with ease. Its always a good idea to get a point in early game so you don't have to worry about anyone being too fast to get away, or worry about getting ganked early on. After is maxed work on your . It helps to get a point early on in this skill as well because it is a good farming skill and its passive is great. Getting mana back for creep kills means your in lane for longer which means more gold and items for you :D. And always remember to throw in a point into whenever you can.

Farming with Karthus is as easy as it gets. Simply walk into a large group of minions and use your to melt away those pesky minions for the gold that you deserve. You can also use .

Lets make one thing perfectly clear. REQUIEM IS NOT MEANT TO BE USED AS A KILL STEALING ULT. Only bad Karthus' use this ult to steal a kill from a teammate.

Here is a list of times Requiem should be used:
-To initiate a team fight
-After you die in a team fight and you feel you need to add more damage if your team is losing
-To pick off a champion that you are 100% sure your teammate can't by alone
-If your teammates ask you to
-If you have Rylai's Crystal Scepter, you can use it to slow your enemies if you see that your team is being chased down

Times Requiem should NOT be used:
-To kill the guy bottom lane has worked so hard to get down, and used their own ults to make sure they get the kill. That's KSing and since your Karthus, you really don't need to be doing that
-When you think the enemy jungle is low and you decide its a good time to use it. (trust me, I've seen this done)

So this section will be dedicated to the items that can counter Karthus' ult . The items that counter are:
- This item is probably the best counter in the game for your ult. It gives the champion a free spell shield every 45 seconds. Considering the lowest cooldown for you ult can be 48 seconds plus casting time, that really sucks.
- Catalyst the Protector This item would require lots of luck, but if the champion just happens to level while your casting, odds are you wont kill them.
- This item gives the champion a free life after death, so make sure you check to see if this item is up or not before you decide to ult.
- This item gives the champion a nice 300 hp magic shield every 45 seconds. Make sure you have enough damage to blast through that before ulting.
- This item makes the champion invincible for 2 seconds when activated. Make sure to check on enemies who have this item often to see if they use it before ulting.

Those are just the items with passives that can possibly counter your ult. This item list does not include items with MR just because everyone knows Magic Resistance is used for reducing ability damage. Also this list does not include items with spell vamp and life steal, as they are not direct counters.

There are quite a few champions in this game that can counter your Karthus ult. Here is a list of all of them:
Alistar's ult makes him take 75% reduced magic and physical damage, which takes out a huge amount of damage. Unless your either 100% sure he used it or he's at 100 HP. don't bother ulting him.
Anivia's passive is a pain for everyone. It gives the champion a free life as long as they don't die in the egg. Make sure to check if this passive is up before trying to take out this champion.
Annie's ability gives here a small armor and magic resistance shield that lasts for 15 seconds. Tho it is a small amount of MR, it might just be enough to save her.
Blitzcrank's passive gives him a barrier worth 50% of his current mana, which in turn will save him a good portion of the time. It has a 60 second cooldown so be very careful when ulting him.
Mundo's ult can regen 50% of his max health in 12 seconds. So if he sees your ulting and activates it you probably won't kill him.
Eve's ult gives her up to 650 health back if she gets a kill or assist. If times right, she can survive your ult.
Galio's ult makes him take 30% reduced damage. If used at the right time he might be able to survive your ult. Also his skill can heal him and combined with his ult makes for a nice defence.
Garen's ability makes him take up to 30% reduced damage for 3 seconds. If used as you ult he can survive.
Gragas' passive restores 2% of his max hp over 4 seconds. This combined with , which decreases damage dealt to him by up to 18% for 20 seconds, could potentially make Gragas a hard champion to catch with an ult.
Its not much, but with the passive on added with her ult she might be able to heal enough to survive.
Janna will be a very tough champion to kill. With her plus her ult , she can not only save herself, but possibly her whole team if they gather in her ult.
With Jarvins skill he can give himself a shield that can stop up to 250 damage dealt to him.
Jax's ult gives him up to 50+ his dodge chance MR. Make sure to calculate this into your damage before ulting.
Karma's plus her heal from can make her and anyone near her hard to pick off with your ult.
Kassadin's passive makes him take 15% reduced damage at all times. And correct me if I'm wrong, but if he can time his correctly he can dodge your ult all together.
If she combines her with her she can take up to 35% reduced damage for 3 seconds, which is the casting time of your ult.
Kayle has a few spells that can help her live through your ult. can heal her or an ally. And her ult can make her or anally invincible for up to 3 seconds.
Her passive can save her if shes brought below 40% health, which shouldn't matter because you should wait until shes lower than that anyways before trying to take her out.
Lee's skill can save both him and an ally from your ult.
Lux's can be used on her whole team to shield them if thrown correctly. Make sure shes off on her own before you try to pick her or someone else off.
His passive shields him for 10% of his max health and comes back every 8 seconds if he is not getting hit. Make sure to catch him when is first gets triggered to deal maximum damage.
Mao's ult can protect his whole team by reducing all damage taken by 20% as long as they are in the circle. Make sure he doesnt have enough mana to use it before you caster you ult.
Yi can be a pain to get with your ult. His gives him up to 300 armor and MR and heals him for up to 700 over 5 seconds. If Yi is good enough, you will end up missing the kill almost every time.
I really don't suggest you ever try to get Morde with your ult because it is close to impossible to kill him. His passive gives him a temporary shield have can take up to 650 damage, and he can keep it full as long as he has minions to attack. Plus is gives him 30 MR for 6 seconds.
Her skill places a shield on herself or an ally, stopping up to 300 magic damage for up to 8 seconds. If you can break through that shield and still get the kill, good for you.
His ult heals him for up to 600 hp. Make sure his ult is down before using your ult.
Nocturne's shield completely negates one enemy spell, and will most certainly be used against your ult.
Orianna's can shield herself or an ally for up to 240. That could be enough to save a foe from death.
Poppy has 2 things that can save her. Her passive can reduce damage done to her by 50% if you will deal more than 10% of her health. Her ult makes her invincible to everyone except her target for 6 seconds. Making her hard to get with an ult.
Rammus' increases his armor and magic resistance by up to 150, which takes away a nice bit of damage from your ult.
Renek's ult heals him for up to 600 health while active. Make sure you can drive through it before using your ult.
Rumble's shield blocks up to 170 damage, and possibly 30% more if he is in the danger zone. Be careful when ulting against him.
Correct me if I'm wrong, but if timed right Shaco's ult can dodge Karthus' ult.
Shen has 2 shields at his disposal. His first one blocks up to 250 damage. And his second shield is his ult can shield both him and an all for up to 750 damage. Be very careful with your ult when Shen is in the game.
Singed ult grants him lots of buffs, including MR. Make sure you can blast through it before using your ult.
Sivir's shield negates 1 spell, and will most certainly use it to block your ult whenever she can.
Skarner's shield can take up to 250 damage. So try to get a teammate to take that shield away before you use your ult.
Tryn's ult makes him invincible for 5 seconds, so make sure his ult is down before using your own.
Udyr's can block up to 220 damage. Make sure you can get past that when you use your ult.
Urgot's shield can block up to 320 damage. Also his ult Hyper-Kinetic Position Reverse grants him up to 130 armor and MR for 5 seconds. Once again, be careful when ulting.
Vlad's makes him untargetable for 2 seconds. Make sure its on cool down or you will never get him.
Wokong's passive grants him an armor and MR bonus of up to 8 per enemy champion near him. Try to get your teammates to back off if your aiming to him with an ult.
Yorick's ult can make it so your ult will make the ghost sacrifice itself and you will not end up getting the kill on your target. Make sure his ult is on CD or he is no where near your target before ulting.
Zilean's ult brings an ally or himself back to life when killed, and grants them a nice bit of health as well. Make sure his ult is on cool down or forget about ulting.

That is all the champions with skills that can help them survive Requiem. Please note the following tho:
-Everything shown here is based on BASE stats, and do not include added help from ability power.
-I generally did not include skills that heal the champion. They are a given and should not need to be listed as they are not direct counters.
-Please be aware that stuns, pop ups, knock backs, and anything like that will cancel Requiem and it will not go off.

First off let me make one thing clear. YOU NEED MID. Stay in your lane and don't bother ganking because thats not what your here for. Once you get start paying close attention to the health of the enemy champs and ult to get kills. If you find yourself not getting kills don't get the until you get more AP. You can use to hit enemy champs inside their turret without getting hit yourself.

Ok so by now you should gave a few kills and at least your and almost your . Team fights should be starting so remember to aid your team because the damage you will be dealing is very helpful.

Karthus should NEVER initiate a team fight. He is far too squishy and will die before anyone can save you. When a team fight should arise start using , but stay on the side lines until most of the people have used their skills. Than run in the middle of it all and use to help the team finish off the champs. To finish off any champs that think they got away pop and continue to push towers with you team.

By now your should be completed as well as your . Now is the time to sell your and buy a . If all is going well you should have anywhere between 15-20 stacks on your and your AP should be in the 900s and everyone should fear you.

Based on how the game is going, obviously other items must be bought for survival, more power, or simply because you feel like changing up your build. Here are some items for Karthus that others might enjoy.
This is a great item that i have used many times myself. It gives you a nice 500 health for when you feel you need more survivability. It also gives you a nice crazy 80 AP and the passive is nuts, slowing champs with your abilities, it's almost like this item was made for Karthus. It is great for team fights, or if combined with your ult, can help your team catch the running champs or be able to get away from pursuers. Buy this item if you feel you need more health, and a wicked passive bonus.
This item is best bought early game because of it's stat gain over time. Just like the Rylai's, it gives you a nice health boost of 450+ an extra 180 when its finished. The mana boost of 525+ 200 is nice if you feel the need to spam your skills. And the 60+ 20 AP is always nice to get for yourself. It's unique passive is a life saver early game, with a nice health AND mana regen when you level up. The nice thing about this passive is that it requires nothing from your end, just the passing of time is all you need.
This item is nice if the other team has lots of DPS. It gives you a nice 50 armor and an amazing 100 AP! The active is what makes this item so good for Karthus, or just about any other caster as well. Being rendered invincible and untargetable for 2 seconds could keep you alive that much longer in team fights. Only downside is that you can not move when this item is activated.
This item gives you a nice 10 mana per 5 sec and 60 AP which isn't bad at all. The 15% cooldown is nice for Karthus. The active however is amazing, hitting them for 30% of their current health, plus 3.5% per 100 AP. If used at the beginning of a team fight it could help you drop those pesky DPS, or if you notice your team is doing a good job focusing them down already, can be used on a tank to take a very nice chunk out of their health.

So a lot of people tell me that Karthus is too easy a champ to use and that I am a noob for using him. They always say he's just around to KS everyone and he just spams all day. Well I'm here to tell you that your wrong. First off Karthus is by far one of the squishiest champs in the game, so survivability is hard. Second, has a small blast zone so you have to be able to predict your enemies movement. Thirdly, is not used for KSing, it is used for times when your teammates can't catch the other champ or when in team fights to help get yourself and others kills after Karthus dies. So don't be hatin on Karthus just because you don't know how to use him :)

And thats the build everyone. If all goes well you should have destroyed the other team and have another win under your belt. Thanks for using my guide. I will keep it updated so you guys can always have the best Karthus experience ever. Comment and tell me what you think. Positive and Negative feedback is always good.

19/05/2011- This passive no longer reduces your time sent dead by 20%. And the ghost time was reduced from 8-7 seconds. An alternate to this is to add 3 points into the Good Hands mastery in utility, but that is all up to you.

19/05/2011- Added a 2nd item build page based more around survivability, but still gives you a nice damage output.

28/05/2011- Added a counter requiem item list and started my counter characters ability/passive section. Posted it half done just because I felt like it.

11/06/2011- Added a few more champions to the counter requiem list. Still is not complete but posted changes. Also thinking about maybe adding a section just for proper Requiem use. What do you guys think?

24/06/2011- FINALLY done my counter requiem lists, for both champions and items. Also Added a section for proper use of Requiem, and a list of when to use it and when not to. Anything else you guys want from me? :p

27/08/2011- Added Skarner and Wukong to the list of champs with counters. Re-added Yorick to the list as well. Also modified the 2nd build by taking out the soulstealer and AA, and added a banshee's and Will of the Ancients. Small added notes to the optional items. Also FINALLY started the section on hard lane opponents. Will finish soon hopefully.

23/10/2011- Added a section with detailed info on Karthus' abilities.

11/16/2011- Upgraded mastery trees now up on both builds.