First off, i would suggest playing Karthus only when in a premade with people you can communicate with over Skype or a similar program, because this allows you to coordinate your ultimate with team members. You could play it in a solo queue if you have very good map awareness, and believe you can keep track of the enemies health bars to a sufficient degree that your ultimate is used in such a way as to max its efficacy.

Karthus can be played as one of the most annoying champions in the game, and if it is done in the correct manner, this turns out extremely well for your team and you. Despite this, as with every Champion in the game, he has vulnerabilities and aptitudes. If your team has need of an AP carry, in many cases, Karthus is a good choice due to the his ability to gank, and simply being a clean up crew to rule all others.

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Pros + Amazing farmer throughout the game + Good Crowd Control with Wall of Pain + If your Requiem is off CD, it is extraordinarily difficult for any enemy to get away with a free kill + Death Defied stops anyone from getting a free kill on you + // Positive attribute here + // Positive attribute here

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Cons - Very, Very squishy - Mana hungry in early game - Squishy... - Quite slow movement speed - Often accused of kill stealing when killing with Requiem - Really squishy...

9-0-21 is a pretty standard Mastery set-up for casters, I take all the Cooldown reduction for obvious reasons, and i take Transmutation instead of Greed because the slight amount of lane sustain is extremely useful. Arcane Knowledge is taken for the extra magic pen. Expanded Mind and Meditation are useful in that they partially solve the early game mana problems. They may be switched for Swiftness , Sage or Arcane Knowledge if you think those will be ore useful.

• Greater Quintessence of Magic Penetration/ Greater Quintessence of Ability Power: The massive amount of Magic Pen provided by gives you a massive early game advantage, and later on you don't need to focus on buying Magic Pen items. I have seen many people go for for the extra Ability Power, but i don't really see it making a difference, so I always get the Greater Quintessence of Magic Penetration.
  
• Greater Mark of Magic Penetration: Look above.
  
• Greater Glyph of Cooldown Reduction: The Cooldown Reduction provided by these runes is essential in late game just to let you cast your Requiem as often as possible, so you don't miss any kill opportunities.
  
• Greater Seal of Scaling Mana Regeneration: I get these instead of Greater Seal of Replenishment, partially because i bought them and couldn't be bothered buying the flat Mana Regen runes, but also because i simply find them to be better.

Exhaust immediately shuts down the enemy carry, whether they be AP or AD. It is a significant slow, and a significant damage decrease. As a Karthus player, enemy Champions like a Kog'Maw with his rang and constant damage output, are extremely dangerous to you in a solo lane, so exhaust helps you either get the kill on the AD Carry, or stop them from getting a kill on you.

Flash... Karthus has no escape skill... Need I say more? The answer is yes. Flash is not only used to escape, but also to chase. If an enemy flashes over a wall on low health, you can flash after them if you take this spell.

Teleport. This can be very useful for any mid lane champion, because you miss less experience, if you are forced back to base you can return without allowing your tower to fall, and it allows you to prevent dirty backdoors from Master Yi. It also provides great ganking options by teleporting onto Sight Ward in the brush and executing a good kill on any lane.

Summoner Spells not to take



Surge does work well on Karthus, but the other spells are much more useful, in almost every way.

Cleanse. Even if you are stunned as Karthus you are still dealing massive damage if you had the foresight to activate Defile beforehand, and if you are stunned and being killed, you are probably too slow to escape anyway, so either way, it is a waste on you.

Clairvoyance should just be left to the support, otherwise you are much more vulnerable, and it is less of a tragedy if the support dies, than the AP carry.

Promote. Just no.

Heal can be useful for defending against tower dives, but if Heal would have been enough to get you the kill, Death Defied will probably do the job for you, especially with Requiem.

• Death Defied: Death Defied is one of the best passives in the game. You are given 7 extra seconds of life to kill the annoying fly that dared touch you. When your build is finished an you have a Guardian's Angel and a Zhonya's Hourglass, you activate Defile run in, use GA, use Zhonya's, and the when you die you can use Requiem and thus even if you get focused, you can take a ridiculous amount of damage.
  
  

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• Lay Waste (Q): Behold! The purple dot of Death! Your early game farming friend and harasser. And your late game massive damage dealer to any number of targets. Double the damage to one target gives you a huge amount of burst in a one on one fight clear away from the minions. When farming with this, always target clumps of minions like the groups of three caster or melee minions. Three or Four of these babies should be able to take care of them, and with Defile, it even costs very little mana.
  
  You will most certainly want to max this first obviously getting Requiem whenever possible.
  
  
  Tips and Tricks
  • Target groups of minions when farming.
  • If harassing, try and hit only the champion for double damage.
  • Don't spam it too often in the early laning phase, or you will run out of mana instantaneously.

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• Wall of Pain (W): An excellent ganking, and Anti-Ganking tool to be used in all circumstances. Provides massive Magic resist and Armour reduction and stops enemies from escaping, and chasing. Unless of course, they are Master Yi, in which case, you lose.
  
  I take one point in this on level two, and max it last.
  
  Tips and Tricks
  • Can be used to zone champions in lane if placed in front of them
  • In a team battle, always place it in the middle of them team, to do as much reduction as possible, and increase your team's damage.
  • To harass, place Wall of Pain, and repeatedly use Lay Waste in front of them while they are slowed.

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• Defile (E): This is what makes Zhonya's Hourglass so powerful on Karthus, it deals over 200 damage per second when the build is done, so if you sit inside the entire enemy team make sure they all start focusing you, and the use Zhonya's Hourglass, you will absorb a large majority of their team's damage, while dealing a massive amount straight back.
  
  You will want to max this after Lay Waste, but before Wall of Pain.
  
  Tips and Tricks
  • Usually turn it on in a team fight, not if you are engaging from the front and they are running, or you will just burn through your mana.
  • In late game, walk into the stacked minion waves with this on and spam Lay Waste to get ridiculous minion kills.
  • Don't use it to farm at all in the early laning phase, otherwise you will find yourself out of mana consistently.

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• Requiem (R): Press R to Kill! But seriously, don't spam your ultimate, unless you are sure can get a kill, or if there is a team fight, you die, and your team needs the extra damage to win. Whatever you do don't panic and cast it when you die, because it will often be a waste.
  
  Tips and Tricks
  • Try to use it at the end of a fight when the enemy team is running and on low health to pick up kills.
  • If a team mate is tower diving, co-ordinate with them to guarantee the kill by lowering their health with this.
  • Do not just spam it at your leisure to keep the enemy's health low, it is a waste of time and mana.

• Sapphire Crystal: The early game mana gives you more opportunities to spam your Q to get farmed, so I always start with one of these plus a Health Potion and a Mana Potion.
  
• Tear of The Goddess: I go back to base for the first time once I have enough gold for these and Boots. Because you will be using Lay Waste very often, it stacks this passive very well. I have seen some people build the Sapphire Crystal into a catalyst the protector, to later build into a Banshee's Veil, and though this does fit into our late game theme of Survivability, the Ability Power and Mana provided by the Archangel's Staff is much more useful.
  
• Needlessly Large Rod: Buying the good old Rod is a very good idea on Karthus, as the massive Ability Power boost provides much needed damage to both Lay Waste and Defile. Building it into a Rabadon's Deathcap is really the only appropriate thing to do afterwards, just for more delicious Ability Power.
  
• Sorcerer's Shoes: Ummmmm, Magic Penetration? Either these or Mercury's Treads against a Crowd Control heavy team, are the only boots for Karthus. You can try other boots if you like, but you will soon come over to my way of thinking.
  
• Rabadon's Deathcap: Plus 140 Ability Power, and an additional 30% of your total AP? This item is a must have for any AP Caster. There really isn't anything else to build your Rod into, so you may as well buy one of these.
  
• Archangel's Staff: Finally, you get the mana you deserve. Now you can spam Lay Waste to your heart's content, and farm entire minion waves in the blink of an eye with Defile. You would be mad not to buy one of these as Karthus, and the extra Ability Power is just a bonus.
  
• Zhonya's Hourglass: At this point, you are THE intitator. You walk into the enemy team with Defile on and Wall of Pain in their midst, and you will be targeted. This is when you press your hotkey, and presto, the entire enemy team takes 200 damage a second, while you stand their with your team jumping in to deal even more damage.
  
• Guardian Angel: This combined with Zhonya's Hourglass provides an immense amount of survivability in a team fight. Engage and initiate with Defile toggled on, allow the enemies to focus their abilities on you, proc Guardian Angel, and once back alive, activate Zhonya's Hourglass if you are being attacked. By the end of that sequence, the enemy will be damaged greatly by your team, you will still be alive and using Defile, and if finally you die, Requiem should be able to finish the fight.
  
• Void Staff: 70 extra Ability power, plus the 40% Magic Penetration that is essential late game to make your Ultimate do that much more damage. I took this instead of an Abyssal Mask because when you cast Requiem the enemy is not nearby to take advantage of the passive, so I find Void Staff to be a better item in this case.

Once you begin laning, after any skirmishes that may occur during the level 1 team fights, I begin by just trying to zone my opponent off the creeps by harrasing with Lay Waste, and once the creep wave is on low health, I cast two or three Qs to kill all three caster minions, and then auto attack last hit the melee minions. This puts you in a quick, but small lead in the CS,which can persist for the rest of the game. After that, lane as usual with auto attacks, which are in fact rather strong on Karthus, and use Lay Waste repeatedly on the groups of caster and melee minions to quickly farm up at least 945 gold to buy a Tear of the Goddess and Boots. At that point, spam your Lay Waste to harass as much as possible while still farming.

When Ganking from your Jungler, team mates and enemies, becomes common, this is when the Wall of Pain becomes a devastatingly useful tool to get kills. When a gank is coming, try and zone the enemy onto the side of the gank using Lay Waste and possibly Wall of Pain and Defile, but I am most likely to save Wall of Pain until the ganker initiates to provide a slow and more damage. If the victim does not have flash, they will probably die, especially if you have exhaust. I would not suggest tower diving as Karthus unless someone else on your team is tanking the tower, as your main damage dealer, Lay Waste is hard to hit a tower hugger with, and by the time Defile kills them at this early stage, the tower will have nearly killed you.

For Late game farming, Defile is one of the most powerful abilities in the game, and eliminates entire minion waves in seconds, while returning lots of mana at the same time. Try never to overextend if Flash and Zhonya's Hourglass are on cooldown, as you are almost guaranteed to be killed. If Zhonya's is up, then you will probably be able to get a kill on the enemy team with Requiem after death, so you can try to push for towers in that case.

In team fights, you are a ridiculously powerful initiator with Zhonya's Hourglass, so always try to be focused by everyone just before you activate it, so when your team engages, the enemy abilities are quite likely to be on cooldown, and you will be dealing obscene amounts of damage all the while. I usually let my Guardian Angel activate before Zhonya's Hourglass, because Defile stays activated during Zhonya's, but not during Guardian, so at the end of a fight, it is better to still be dealing damage rather than respawning. Never forget to place your Wall of Pain before you initiate to enhance your team's damage, and remember to use Lay Waste when invulnerable or respawning. If you have depleted all of your active item effects, you are on low health and your team should be able to mop up the rest of them, when your last active ends, use flash to put some distance between you and the enemy team, and if necessary, use Requiem. You may be Suicide Karthus, but you must still avoid death as much as possible.

I do play using this build very often. It is common for me to be weak early game, and die a few times, but in late game, it is very easy to pick up Double, Triple, and occasionally Quadra kills with Requiem using the Suicide Karthus stratagem so don't worry if you get off to a rocky start.

Last thing, thanks to JhoiJhoi and JhoiJhoi's Good Karthus Guide template for helping me with the sometimes very confusing BBCodes. My guide would look ****py without the help of that guide.

One game we lost, but played very well. Went for 74 minutes.