Message to all viewing this Build i will leave it up for awhile but im going to change to a new build.

I know i made this build a long time ago when dinosaurs roamed the earth. I started to edit this guide but I'm just gonna start a new one

Argh... seems as if <list> Tags would not work in comments. Sorry for the ****ed up design, was rather supposed to look like this (maybe you can delete the first comment?):

-Exhaust and ignite wont grant you any survivability nor map control. You will have problems to be back on you lane fast, after getting killed.

- You are sacrificing "presence of the master" for improved ignite? That is 17,6% more cooldown time for your summoner spells as needed. For 10 AP - bad trade.

- You waste your runes on cooldown reduction - why? It only affect your *** and your requiem - are you one of that nasty kill stealers that need the ulti ;)? It wont really affect lay waste (as it has already a 0,87s cooldown after masteries), and defile has no cooldown at all.

- 1.300 mana is way to low, you should aim at 4.000 mana at least. You will want to have defile on very often.

- You should focus on defile more. Skilling Q, E, W, Q, E, or even Q, E, W, E, will grant you great harrassing potential on mid lane - and first bloods even greedy Mordekaisers. But that needs mana ;).

- None of your items contains a catalyst the protector. This is an excellent item in early game on mid lane, as it restores mana and HP on lvl up. Grants you survivability -> lane presence.

- Your magic penetration is too low for the costs by the items you have chosen: 39,97 is nice, but you let go plenty of AP for that. In this AP/MP build you might get an idea, how to optimize your build.

- Rylais is a bad choice to get HP and AP, as long as you have no rod of ages before: 80 AP as well, even 650 life and 725 mana.

- With that squishy build you rely on mejais... in worst case, if you get no stacks due to dying to often, you have 362,5 AP. Changing Zhonyas to an archangels staff, would mean 416 AP and 2.700 mana already - you should only buy an Zhonyas, if you have plenty AP already. This build hasn't.

First of all: Nice, that you thought about a Karthus build at all. But

• Exhaust and ignite wont grant you any survivability nor map control. You will have problems to be back on you lane fast, after getting killed.
• You are sacrificing "presence of the master" for improved ignite? That is 17,6% more cooldown time for your summoner spells as needed. For 10 AP - bad trade.
• You waste your runes on cooldown reduction - why? It only affect your *** and your requiem - are you one of that nasty kill stealers that need the ulti ;)? It wont really affect lay waste (as it has already a 0,87s cooldown after masteries), and defile has no cooldown at all.
• 1.300 mana is way to low, you should aim at 4.000 mana at least. You will want to have defile on very often.
• You should focus on defile more. Skilling Q, E, W, Q, E, or even Q, E, W, E, will grant you great harrassing potential on mid lane - and first bloods even greedy Mordekaisers. But that needs mana ;).
• None of your items contains a catalyst the protector. This is an excellent item in early game on mid lane, as it restores mana and HP on lvl up. Grants you survivability -> lane presence.
• Your magic penetration is too low for the costs by the items you have chosen: 39,97 is nice, but you let go plenty of AP for that. In this AP/MP build you might get an idea, how to optimize your build.
• Rylais is a bad choice to get HP and AP, as long as you have no rod of ages before: 80 AP as well, even 650 life and 725 mana.
• With that squishy build you rely on mejais... in worst case, if you get no stacks due to dying to often, you have 362,5 AP. Changing Zhonyas to an archangels staff, would mean 416 AP and 2.700 mana already - you should only buy an Zhonyas, if you have plenty AP already. This build hasn't.

So keep up your work, but I prefer not to vote on this build yet.