Im going to start off by saying: A lot of the ideas in this guide are from some of the top rated guides. I have my own twist on the item sequence, so I figured Id share it.

I took Magic pen marks because all of malzahar's damage is magic based hero and it really helps get past their magic resist.

For Seals, I grabbed cool-down reduction. This brings up his ult up quicker and helps with his other spells as well.

For glyphs I took ability power per level. It never hurts to have the extra AP.

First, grab a Doran's ring and head out to mid. Doran's ring will give you great mana regen and some extra AP early.

If you get the chance to back do it to buy your sorcerers shoes. The magic pen is great.

Next comes Mejai's, make sure not to get this item too late or you will miss out on stacks.

As soon as you can grab that Abysmal scepter. Not only is the MR great but the additional magic pen and AP make you very dangerous, especially if you have some stacks.

Afterwards, head back and pick up a Rabadons. When building a Rabadons, I get the needlessly larger rod first, makes it seem less expensive.

Finally if you get to it grab a will of the ancients. The spell vamp is nice along with giving your team some extra AP.

If the game keeps going, and they are stacking MR sell that dorans and grab a Void Staff. That should keep you dangerous.

Malefic Visions: I choose to max Malefic visions first because it has the best farming potential. Especially if you are mid. However I dont really cast it on minions until I am about level 5 or so. It doesn't do enough damage to keep the chain going and can waste mana.

Null Zone: I only take one point in this early because it is so easy to dodge and does little damage to minions. Max this last.

Call of the Void: this is a great tool in team fights because it can silence large groups. It also causes great damage. I try to harass with this early if possible. But not too often or you wont have any mana.

Nether Grasp: Finally your ultimate is awesome. Try to put your null zone and malefic visions on them first then ult them in the pool. Its almost a guaranteed kill if you have harassed them at all.

As I said, this is my first guide and I would appreciate feedback. Just doing this because I havent seen a guide with this build. Plese feel free to comment with any ideas. Ill check this periodically and update it.

Early Game: Try to harass the enemy champion with your Call of the Void. It does decent damage and the silence can prevent a counterattack. Try not to over use malefic visions early because it lacks the power to keep the chain going. As you level it up more then use it. If you find it hard to keep the chain going past the cannon minions dont be afraid to use your Call of the Void to put down the stronger minions.

Mid Game: By now you should have your boots and mejai's and be working towards your abysmal scepter. If you have a few stacks start harassing and then you can start ganking. Ping your team so they know and cast that ult to get a guaranteed kill.

Late Game. By now you should have most of your build. The key in team fights is to stay in the back. Try to line up your Call of the Void to silence multiple opponents. your null zone will also take great amounts of health from the tanks. and of course try to suppress their carry with your ult. Using Malefic visions when possible.