Hey everyone. This is a guide for carrying your team as an AP Mid. Most people classify Karma as a support. I think that's the real problem. There are better supports, at least early game. Karma's abilities are all AOE, so she's losing a lot of damage if you are only with a single teammate. She also needs farm more than other supports. Enough of this support stuff. Let's talk about her as an AP mid.

Karma has a few things going for her, and a few things against her. Let's take a look.
Pros: Full aoe spells mean massive damage in teamfights
2) Passive can be used for baiting and can save you when low. Also stacks with Rabadon's.
3) Many people don't know how she works or they underestimate her since she's a rare pick.
4) Possibly the best Ap farmer aside from Morde.

Cons:1) No hard CC. W is a slow and can be useful but you won't be interrupting any enemy spells with it.
2) Ganks are bad. Since you'll be mostly upgrading Soul Shield and heavenly wave, you won't have more than maybe a point in Spirit Bond, so her slow is going to be nearly useless.
3) Many people don't understand your spells. For example, I had a tristana get ignited with about 100 hp jump AWAY from me (no idea why) when i could have easily shielded here and saved her. Sometimes it helps, at the beginning of the game, to say "Hey, if you get are really weak RUN TO ME so I can save you".

REVISED: After much testing I've changed my build quite a bit. Read this part!

Use magic pen MARKS
AP per lvl SEALS
FLAT Cooldown reduction GLYPHS
And MOVESPEED QUINTS (combined with masteries you will be as fast as most players that have t2 boots when you only have boots of speed)
This allows you to safely get a Doran's Ring first and still have some speed if you get ganked or need leave mid lane.

I use to get flat mana regen seals, but I find that with 2 Doran's ring early it's enough mana regen to get by.

REVISED: Please read

Go 21/0/9. You need the ap and 6% bonus damage to help with last hitting and when enemies are weak. You ARE the AP carry after all.
In the utility tree, you need to get the movespeed masteries, all 4 points. This will make it much easier to get out of bad situations, to catch up to fleeing enemies, and to still stay fast before you finish your boots. Overall the speed is definitely worth it.

Don't forget the bonus buff length mastery, that helps a lot since early you will taking blue a lot and late game when you have Baron.

Your item build is going to be the same, at least early game, for nearly every game you play. You are rushing Rod of Ages.
Start with a Doran's Ring. I pick this over boots, because you already have sustain with your heal and the more you can shield/heal the better. With your movespeed quints and masteries you don't need the speed from boots as much as you need the mana regen, ap, and hp from Doran's Ring.

The first thing you are getting when you go back is buying a second Doran's Ring AND Boots AND 2 wards.. This will cost you 475 + 350 + 150 for a total of 975, Make sure you have AT LEAST 825 so you can at least buy boots + ring. Wards are highly recommended but if you are super careful not to push your lane you should be ok.

On your second back, buy a Catalyst the protector. You need 1325 for it, and hopefully you will have about 150 more so you can buy 2 vision wards. Place it where you normally guard blue from bevore minions spawn, and the other at the other side of the river, same place.

The next time you go back you should have 1710 for Rod of Ages. Again, buy a ward or 2, and continue farming to finish your boots. If you NEED speed, finish boots before RoA. It's a trade off though, as the earlier you get RoA the better, as you want to start getting the bonus hp/mana/ap as soon as you can. I highly recommend finishing Rod of Ages before boots. Like I said before, with movespeed quints and masteries you should be moving as fast as everyone else with T2 boots.

Finish your boots OR if you can grab blue, just rush Rabadon's. If you don't have blue I recommend finishing boots for the CDR, or get a fiendish codex to help start your Athene's Unholy Grail. It's a GREAT item for Karma. After Rabadon's get Athene's, then either
A) Void Staff if they have a lot of MR
B) Abyssal Scepter if you drastically need MR
C) Rylai's Crystal Scepter if you think the slows would be good in fights (they are)
D) Zhonyas if you need the armor and you're against someone like Karthus. (When he ults, shield an ally, then use Zhonya's. Now 2 people have avoided taking damage.

Late game you will want to have
Rod of Ages Rabadon's Deathcap Athene's Unholy Grail Rylai's Crystal Scepter Void Staff Ionian Boots of Lucidity

You want Soul Shield first to help your jungler get wolves or wraiths and leash blue/red, and for harass in your lane. At lvl 2 get wave (Heavenly Wave. I may refer to it as just "wave", or "heal").

This is when you need to make decisions depending on what you need. Even though your passive gives you extra ap the less hp you have, you don't want to be laning with less health unless you are 100% sure their jungler is not going to gank you and you can withstand a full combo from the mid against you. If I have nearly full HP, max shield (E), since it does more than wave, and you don't need the heal. If you have less hp than you really think you should have, max wave instead to help get your hp back up.
Get Spirit Bond at between level 4 and 11, depending on how early you might want to gank or avoid a gank. I usually get it at about level 7, give or take a level. If they have an aggressive jungler, get Spirit Bond early to help you survive a gank. If you think your lanes are ok, and want to continue farming, forget W and just max shield/wave. This gives you max damage and speed for clearing creep waves and wraiths. Which brings us to farming . . .

Karma is the best Ap farmer in the game other than maybe Morde. During a really good game, you will have *more* than 10 creeps per minute. AKA, I've had 200 creeps at 19 minutes before. It's pretty funny when the person you are against has maybe 130 when you hit 200. If a lane is pushed, try to coordinate with your jungler to gank. Bond your ally to reduce the time needed to get to that lane. Slow your enemies with W, and if it's a single enemy running away, try using a mantra+spirit bond to slow them drastically.

Before you hit about level 5 or 6 you should just be last hitting creeps with your attack. After that, you can walk into the middle of a creep wave, and mantra + shield yourself, and then wave the creeps still alive. Do this when farming wraiths too. Ask your jungler first but they should say yes.

During team fights you have a few options at your command. Your best option is usually to speed up a tank, like Singed, to initate a fight. If you are tanky enough, you can Spirit Bond an enemy and walk straight into the enemy team (make sure your team comes with you!), shield + mantra yourself, and then wave as many enemies as possible. A safer bet would be to let your tank go in first and then shield + mantra the tank, and use your Q when you can. If you are already in a fight, use your W to bond an enemy or ally that is between you and a lot of enemies. That was you can walk sideways and force the beam on your enemies, slowing them and dealing damage. Try to get as many people caught in the beam as you can, as it speeds up both allies and slows enemies.

When you don't need to, or you can't get close enough to Q an enemy, focus on healing your teammates. Prioritize healing your weakest teammates first. Heavenly Wave (with mantra) heals the most when you have the least amount of health. If your team does not know how Karma works, make sure they know to get in a cone when healing is needed. If you can heal all 4 of your teammates, if will dramatically increase your sustain and allow you to push towers more easily.

When taking towers without creeps, have someone tank the tower and then Soul Shield them. If your tank is still not tanky enough to survive, be sure sure to rotate who tanks the tower to minimize the damage from the tower. Heal those you need it and keep shielding. You can also shield minions when taking towers, and if you shield a siege minion you get more bang for your buck since it takes only 50% from the tower anyway.

Late game, if you are not fed or you are not the primary source of damage, make friends with your AD carry. Follow them around, speed them up constantly so they don't get caught, and shield them during fights. Late game your shield should block upwards of 700 damage. Keep your squishy alive and you will win fights.

(Personal note:
If you can have a Soraka support on your team, it can make your AD carry nearly invincible late game. Soraka will heal and give your AD carry lots of armor, while you will give them a huge shield to soak up damage, and you can ALSO heal. (Substitute Janna or Lulu for mega-shields.) Your ad carry will love you and your support. Also, if your AD carry has lifesteal, you can shield them at 200 hp, and they will have time to get some of their health back without your heals.
Second note: Spirit Bond a Skarner for instant lolz. It's fun having a pet scorpion)

Overall, this build should help you play a viable mid Karma. Make sure you farm hardcore, and call mia and make sure your teammate listen. Keep to your core items (RoA and Rabby), and then build what you need. Good luck!

P.S. I highly recommend referring to the Comprehensive Karma guide. It has a ton of useful information and there is no reason for me to try to replicate it when I can just refer you to it. However, the information in it is mostly for playing Karma as a support. Learn from it, but use this build, and you should do well.

April 30, 2012
Updated to include change from Sorc. Shoes to CDR boots as recommended boots.
Added more to items section.
Adding tags to make everything look better . . .

May 4, 2012
Changed recommended seals to AP/lvl.

May 24, 2012
Lots of changes to various sections. Updated items to include Athene's Unholy Grail and Darius patch.