Hello everyone, and welcome to my first Mobafire guide! In this guide, I'll be teaching you guys the in's and out's of Karthus, the Deathsinger.

Karthus is a fragile champion, but can do insane amounts of damage when played right. That being said, here are some things to remember:
-Well placed Q's can make (or break) Karthus. Late game Q's can hit up to 500 magic damage every second.
-Karthus' passive (Death Defied) is broken and should be used in team fights.
-Your ult is not just to kill steal. Use it in the beginning of team fights and if you really need to, ks afterwards with your Q.

Pros:
-One of the highest DPS AP champs
-One of the best AOE slows in the game
-Sustain with E passive
-Very valuable in team fights with passive
-Insane farming skills
-And, of course, his global ult


Cons:
-Extremely squishy
-Hard to play
-Long cooldown on ult
-Easily countered
-Item dependant

Marks:
Greater Mark of Magic Penetration
As for most AP champs, magic pen runes are preferred.

Seals:
Greater Seal of Scaling Mana Regeneration
Mana regen is a good choice for Karthus mainly for levels 1-3 when you don't have a Tear of the Goddess yet.
Other alternatives include: Greater Seal of Scaling Magic Resist and Greater Seal of Magic Resist for laning against other strong AP champs.

Glyphs:
Greater Glyph of Ability Power
I like flat AP glyphs because I usually run MS quints instead of AP quints.
Other alternatives include: Greater Glyph of Scaling Cooldown Reduction

Quints:
Greater Quintessence of Movement Speed
I'm a fan of MS, so these are my preferred quints for most everyone I play.
Otherwise, use Greater Quintessence of Ability Power

Skill order of importance:
Requiem > Lay Waste > Defile = Wall of Pain

Note: Defile and Wall of Pain should be leveled depending on the situation. For example, if you have a jungler like Lee Sin who can gank at level 2, level Wall of Pain before Defile. If you are using too much mana, get Defile first for the passive. Later on, level whichever skill you find yourself using more (but remeber, requiem and lay waste come first).

Flash
This spell the most used in the game. It's a great way to escape dangerous situations and is especially valuable for a squishy like Karthus. Flash is also valuable for teamfights--you can flash in, do damage, get focused, and activate your dumb passive (explained in depth later).

Teleport
This spell is useful for and DPS AP champion like Karthus. Ignite is not needed because a couple well-aimed Qs will be the same as an ignite. Instead, you can coordinate pro ganks in other lanes and carry your team.

Other options (substitute teleport)
For those more sustain early game
For securing kills/ +5 AD&AP from mastery / heal reduction
For extra baiting power

Start off with the standard boots and three potions or a mana crystal and potions.


Then rush Tear of the Goddess, preferably by your first time back to shop. Tear of the goddess is extremely useful on Karthus, especially with the high spamability of your Lay Waste. By level 4 or 5, you should have blue and should be filling up your tear of the goddess. Since Lay Waste is Karthus's main damage output (no, his main damage output is not Requiem), you should fill your tear of the goddess completely by late game. This translate into a ton of AP, along with your Rod of the Ages.

sorcerer's boots or boots of ionian lucidity
Sorcerer's boots are extremely good early game, but fall of late game. If you go sorcerer's boots, you end up doing more damage than getting an AP item such as Blasting Wand. If you decide to go CDR boots, grab some AP first in order to do some damage. (If you go sorcerer's boots and you reach the end of the build, switch your boots out for CDR boots).


Blasting Wand
Grab some quick AP, later built into Rod of Ages

Rod of the Ages
Rod of the Ages
This gives some greatly needed tanky-ness to your build. In competitive gameplay this is a must. This also contributes towards your AP late game when you buy an Archangel's Staff.


Rabadon's Deathcap
More AP!


Void Staff
Some greatly needed magic pen (especially useful for Requiem.


Archangel's Staff
At this point, you'll have a full tear of the goddess and a fully charged Rod of Ages. Finishing your build with one or two archangel's staff will give you tons of AP.

Rylai's Crystal Scepter
This is helpful for hitting your Q's and gives you extra health. Very useful if you didn't buy a Rod of Ages


Will of the Ancients
This is an item most other Karthus builds have. I explain in the next section why I never buy this item for Karthus. If the range on your Q isn't long enough resulting in you taking unnecessary damage, then take this item early in your build


Morello's Evil Tome
This item offers nice CDR and mana regen. I never really liked this item on Karthus but feel free to experiment with it.


Zhonya's Hourglass
The passive on this item is great for many AP users. However, I don't usually run this item for similar reasons to Will of the Ancients.

A lot of other guides rush Hextech Revolver for the spell vamp. Since Karthus is a squishy champ and does tons of AoE damage, spell vamp seems like a good idea. However, this sacrifices extra AP, and as Karthus, you need all the AP you can get.
Having spell vamp also decreases the usefulness of your passive. When you die, the extra AP will greatly increase the chance of you getting a return kill, or even a double (from the enemy laner and jungler). I've had many Xin Zhaos tower dive me only to feed Karthus the double.... However, without spell vamp, managing your health becomes an issue. With lower health, Karthus' passive makes him an excellent baiter.

The difference is basically doing more damage, or do less damage but last a second or two longer (alive).

Early Game:
Karthus doesn't have a very good early game, especially levels 1-5. At these levels, you should be hugging tower and farming. You can throw out occasional Qs to harass but early game for Karthus should be centered around farming. Getting a creep kill is more valuable than doing 100 or so damage to the enemy laner.

Mid Game:
Once you get your ult, Requiem, always keep on the look-out for low health enemies. Do not trust your teammates to tell you because about 50% of the time they won't. If you have your Teleport up, you can push your lane and teleport to other lanes where the enemy jungler has ganked (or when the enemy team is past your creep wave) and pick up an easy double or triple kill. If your jungler hasn't given you blue buff yet, now would be a good time to ask for it.

Late Game:
This is around level 16, or whenever the laning phase is over. Remember your Teleport and get ready for teamfights. Once your tank has initiated, walk/flash in and toggle Defile. If you can, split the enemy team with Wall of Pain and constantly spam Qs. At low elos, chances are you will get focused and your passive will get activated. Even if the enemy team is at low health, use Requiem and after your Wall of Pain to allow your team to chase or get away safely. After that, spam Lay Waste.

Who counters Karthus? Who does Karthus counter?

Who you do not want to lane against:

Ahri
Once you get hit by her charm, it is all over for you, especially since she can ult out of your passive.


Leblanc
Like many other AP champs, leblanc hard counters you with her insane burst and silence.


Veigar
Basically self-explanatory. His ult scales with your AP and has insane burst.


Kassadin
Similar to LeBlanc


Zyra
A well played Zyra can absolutely destroy Karthus with her overpowered plants and stun. Almost impossible for Karthus to even harass without almost dying.


Katarina
Her Shunpo can dodge your slow, Lay Waste, and passive.


Fizz
His high mobility can avoid many of Karthus' moves. Similar to Ahri and Katarina


Who you do want to lane against:
Karthus does not directly counter any typical AP champions, but he is very powerful against AP champions who do not have high mobility because of his Q and slow. Karthus is known for being strong mid-late game, and not so much in the laning phase unless helping top or bottom with his ult.

These four builds are something I've done before and have worked out nicely. Items like Abyssal Mask and Zhonya's Hourglass are very nice resistant-providing AP items that go well with health AP items such as rod of the ages and Rylai's Crystal Scepter. These items are good when you aren't exactly high on creep farm and kills. You are a little more tanky (which makes it easier to prevent feeding the other carries) while also providing some utility for your team with the items' passives. The four alternative build is a revive-teleport build. I haven't built this directly, but I have gone to that build in a 60 minute game where I finished my initial build. The damage is incredible, but I wouldn't normally recommend doing that right off the bat.
It is a suicide based build and is very hard to play without feeding.

-Your passive is arguably one of the best in the game--don't be afraid to use it in team fights.
-Don't ult just to kill steal. Using it in the beginning of team fights gives your team a huge health advantage.
-Don't push your lane early game. Karthus is a squishy champion. Many AP laners such as Veigar or Zyra will destroy you if you get too close. Utilize the range of your Q and stay near your tower while farming until level 6.
-Hitting your Qs is one of the most important things you can do as Karthus!

Thanks to jhoijhoi for her guide on making guides
Thanks to iamblamb for a helpful critique of my guide
Thanks to Ohyeahyeahyeah for his passive aggressive suggestions on my Karthus gameplay

Also, check out NubbiestN00b's riven guide: http://www.mobafire.com/league-of-legends/build/riven-has-a-cute-top-235882

7/30/12 - Created the guide
8/11/12 - Changed around masteries, added counters
8/19/12 - Reached 72% rating, added change log
9/25/12 - Reached 11k views