Pretty much, this is a Malzahar build. It's pretty well rounded and easily modified. It's probably not the best, but it's worthwhile. If even you choose not to take it into an actual game, atleast use it to get an idea of what to build.
I've found building him flat damage at early levels does about the same as building him tanky. Even buildingRod and Doransx3 you still have plenty of damage. The Mask of the Illuminati and the and the Pimp hat maximize your damage, while the Frozen Broom stick Makes you a permaslow and helps the Illuminati Mask. The Angel is more of a defense items. I'll get into that in detail later.
Runes & mastries are essentially any AP Carries runes.

Malz is one of the Old School mages, like
Ryze,
Gragas,
Kassadin,
and Veigar.






You can play them on two different ways. You can push your creep hard then roam and gank. Or you can push your enemy out of lane and just hard push your lane until you reach inhibitor. Depending on what route you choose you might have to buy a few in and out items. Wards and Elixirs..


He's Pretty dynamic and has quite a bit CC and DoTs. He's one of my favorite Heros and is quite fun to play. He can melt other Heros and farms very quickly.

Malz has lots of CC and DoTs.

Let's go deeper into Each Ability.
Summon Voidling









This is his passive. Every few spells you summon a minion to fight for you. After some time it gets stronger. It targets whoever has Malefic Visions, so make sure to get MV on your main target. It also makes minion farming a breeze. A Nice passive.

Call of the Void









His Q is a strong ability mainly for CC and damage. You can use it in unique situations, sometimes in areas where they can't dodge. Very strong, I've had it hit champions for half their health.

Null Zone









Area of Effect huge Damage. I max it last, as it deals a nice bit of damage at level 1, and your AP will scale it where it needs to be. Use it with your combo for massive damage potential. %Max Health Damage.

Malefic Visions









Huge DoT and great for everything. This is his bread and butter. Harass, sustain, creeping, killing, everything is off of this skill. All of his other abilities scale into one way or another. Especially with the Mask of the Illuminati it's huge Damage.

Nether Grasp









Huge CC Damage, Long Suppress, massive damage, scales into a massive Combo that can kill just about anyone.

Start:




Why? Doran'sx3 Max huge sustain with it's passive restore mana stacked with Malefic VisionsPassive
First back:




Why these? Well boots and catalyst Don't need explaining. Wards are for if you plan on hard pushing Mid. That means past first tower. The Elixir is for if you decide to roam and gank everywhere, for a bit of extra AP and CDR.
Second Back:



Okay. You want the Spiked Rod as soon as you can get it. Then you want the Mardi Gras mask, then upgrade it to The Mask of the Illuminati as soon as you can.
Late Game:




Pretty much every Other item that will do well on him. I'd rather get the Pimp Hat>Frozen Broomstick> Angel. Mainly For damage, CC & life. Frozen Broomstick maxes the Mask of the Illuminati's potential. Pimp hat for damage, and Angel for life. Everything else works like a charm too.

Minion Farming->









Skirmish- >








Single Target Nuke - > > ___ [img=http://images4.wikia.nocookie.net/__cb20110416190420/leagueoflegends/images/b/bc/Nether_Grasp.jpg