Hi people. I have been using Karthus for a while and i think hes the best character i ever used. Most of the guides i see are mostly weak ap. My guide is for people who prefer killing instead of farming.

Pros
-Very good at harrasing .
-Overpower ult (if you know how to use it)
-Great farmer
-One of the best passive skills in the whole game
-When u try to gank him he can use wall of pain to run.
-Lay wasted 1 sec cooldown
-Best at mid


Cons
-Needs to be fed To be good.
- Very squishee

-This skills mean when u die u can spam all your skills for 7 sec and u dont need mp just spam(u cant move).Before u die use all of your skills so when your dead use your ult to kill them all.
-This is your main skills and harasser skills.IF u know how to use it for farming with defile(when toggle off)u can relly spam this skills with out recalling.
- THis is for chasing and fighting. This can lower magic resist so your skills do more damage.
- This is your skill that gains mp and dps skill. Do not use it when u have low mp it drains your mp fast.When your dead keep this skill on it wont use any mp and it can kill people when they are near it.
- This skill will make others rage like hell. It hits the whole place. If u have void staff it will go through there magic resist and most do about enough damage to 1 hit kill if they are 1/4 hp.

- I use flash because you can escape with it or chase.It work great with defile.


- This skills is very good.you can go to anywhere in the map fast and if u recall u can go back to your lane fast.


- I would use ghost because u need to chase and u can use it if your not the right lev for flash.

To start harrasing u need to use your lay wasted. Start going near him and spamming it near them. Then keep doing that until they leave the lane to recall or if they fall back.

To use Karthus u need to go behind your minions and start normal hitting their minions.When they are about to die use your lay wasted. If the enemy champion trying to farm off your minion start harrasing them. Then when they leave to recall start pushing. look out for ganking on the mini map. When your level 5 then u can start fighting other champs. To fight use your wall of pain on them to slow them down and lower there magic resist.Then use defile near them and chase them.Then start spamming lay wasted in front of them.If they get out of your defile use flash or ghost.If they run behind the turret use your ult and it should kill them.

Most of the runs i pick are for magic penetration so your ult do more damage and the other 1 is for mp.

First buy the boots and 1 hp pot and 2 mp pots. Then buy meji. Meji will be your first core item. This item will make u have to take a lot of risk but if u know how to kill and use your ult right it can be very rewarding.Then buy the rod of ages for more mp and hp and ap.Then buy death cap to make your ult have more damage.Then void staff early so when they build magic resist u have magic penetration.Then buy zhonya's hourglass to help u block your enemies ability and then last will of the ancients.Then your set to go.

To use requiem u need to look around the map.If u see a person with low hp use it or if your team is chasing someone.If your team is going to push and try to kill use it and your team can finish them off. Heres the amount of hp an enemy should have before using requiem at its level.
Requiem lev 1. use when enemy has this much(0-210 hp)
Requiem lev 2. use when enemy has this much (0-390 hp)
Requiem lev 3. use when enemy has this much(0-480 hp)