This is my build for Malzahar. As with nearly all Malzahar builds, and because Malzahar doesn't play well with others, it is designed for center lane. The idea is to maximize damage output without being completely squishy. I have found it to be very successful against almost all teams and usually only requires minor changes to counter the enemy team.
For marks, I go with greater marks of insight. These are probably the best marks for your standard mage. I would not recommend going with any other runes. MR does not scale on most champions and must be purchased. They can drastically increase your damage at low levels making you do near true damage.
for seals I like to get a combination of mana regen per a level and straight mana regen. Its true you can gain mana from malefic visions, but i find that these runes allow you to spam a little bit more and get more minion kills as malefic visions doesn't always get the kill. Not to mention more spam=more voidlings, gotta love those little guys. Some people use 9 mana regen per a level. I like to get a few straight mana regen so im not hurt for mana early game. Get whatever suits your playstyle best.
For Glyphs, I like greater glyphs of focus. Cooldown reduction means for damage output and more voidlings. Cooldown reduction is a must for malzahar. I prefer straight cooldown over cooldown per a level as the cooldown per a level takes too long to be on par with the straight cooldown runes. Some people argue that Malz is better at high levels and therefore per level are better. My theory is that the straight cdr runes allow me to get more fed at low levels making me stronger all game. straight cdr runes and morellos evil tome should give you plenty although cdr per level will bring you closer to max cdr, get whichever you like.
Probably my favorite quintessence are AP. They make you that much stronger early game, allowing you to dominate your lane. I have seen people run health quintessences. They are good too, I just don't find them quite as helpful.
My favorite item to start with is Doran's ring. Gives you everything you need, mana regen, HP, and AP. Boots and health potions are okay but i find Doran's more helpful.
Rod of Ages is my next item. The Catalyst helps you to stay in lane for longer. Not to mention the bonus health and mana. The AP also helps alot. I find it to give you alot of sustain while bringing your AP up significantly.
Boots are needed next or you will never catch or get away from anyone. Sometimes i get boots of speed before i finish the RoA other times i finish the RoA first. all depends on how fed I am and how much i go back. I would make sure to get your sorcerers shoes before going for Rabadons though. I find Sorcerers shoes to be the best choice since we aren't ussually going for a void staff. CDR boots are an option, mpen is a bit more helpful imo though.
Rabadon's is up after Rod of Ages/boots. Although some people rush this item instead of Rod, i find those builds to be incredibly squishy and not that effective. Malzahar has no abilities that help him escape, so unless you can power through an enemy or are close to a turret, chances are you are not getting away. Rushing Rabadons simply makes you to easy to kill. That being said, Rabadons is an AMAZING item once you have the proper health and mana thanks to RoA. This is a must have item and will skyrocket your AP. A second reason for getting it after RoA is that your RoA will be much more grown once you get your rabadons making your AP much higher than if you got it in the other game. This will greatly help your mid game.
Next i usually get a chain vest and a negatron cloak, getting whichever is more necessary to counter the other team first. If they have no fed AP or no fed AD, i may only get 1 of these and hold off on the other. These items provide the defense needed to not be a total glass cannon. Additionally, they aren't very expensive.
Gives you some nice cdr for relatively cheap, and is also the precursor to your Evil Tome. I like getting it after the defensive items as i find it slightly less important than them but still incredibly helpful.
This is where you have some order choices to make. I generally go to a Abyssal Scepter, Evil Tome, or Zhonyas at this point depending on the enemy team.
Morellos is my favorite to get next. Gotta love that CDR. combined with the runes it brings you to about 30% CDR, a bit more if you go with CDR per level. combined with the mana regen, it allows you to spam your abilities, which means more damage and more voidlings.
Abyssal Scepter is my 2nd favorite to get next. The boost MR is better than the boost to armor from Zhonyas and it is alot cheaper. although zhonyas gives a bit more AP, the passive of abyssal helps your damage output as well as other people on your team.
I ussually get this last. Its a good source of AP and Armor and a good item to have. Its active can also save your life if timed well. i get it last simply because other items also give damage output and we already have chain vest at this point to give us some armor. Build it earlier if you like or if you really need the 5 more armor (although i don't see this helping too much) or if you want the active.
On other items:
Void staff is viable as always, i just find it less useful than other items. between our mpen runes and masteries, our boots and the aura on abyssal scepter i don't think its the best choice. That being said, if the other team is stacking MR because you are wrecking them its a good choice. If i get this i ussually don't build the abyssal scepter as it makes abyssal's passive unecessary. Unfortunately that means no MR bonus.
Archangels staff is also a good item. Lots of mana and lots of AP. I just think it takes too long to build and I would rather gain Health/ MR/ Armor/ CDR. between your runes, RoA, and Evil Tome you will have plenty of mana/ mana regen. Im rarely oom at high levels. Get it if you really want it, but it means you will be alot squishier as you will be dropping an item that provides AP and defense.
Banshees Veil is a good item and the passive helps, but I don't like the lack of AP when you can get more MR from abyssal along with 70 AP.
Rylais is meh. the slow is nice since we have none of that, but its only 15% since all of our abilities are aoe or dot. 15% slow is just not worth 3100 gold Imo. health is nice, but we get that from RoA and MR and Armor get the same job done. Its good on some characters, I just don't like it on Malz.
Have only tried Will of the Ancients a few times. Its kinda cool as ulting in your W will bring your health up drastically. I just find it a bit hit or miss. It can heal you quickly, but 1 cc and your likely to be dead without the defense of other AP items you might get instead (abyssal or zhonyas). no doubt a good item and you might want to experiment with it.
I get Call of the void first, Malefic visions just doesn't do much at level 1 and can't be taken to level 2 until Malzahar is level 3 anyway. Additionally, you can spam Q on the summoner platform 3 times so that your first ability in lane makes a voidling.
Malefic visions is your most important spell early game, it farms, harasses, controls the lane, and gives you mana. Level it as often as possible.
Null zone is greater for taking down tanks. because it does % damage it remains effective at level 1, allowing you to level it up last. I generally only use it in team fights, when i plan to ult or when i am spamming to take some1 down fast, otherwise malefic visions or call of void will serve you better. Its not that greater for killing minions compared to your other skills. Great for killing blue buff though.
Nether Grasp (Ult) - as with most ults. Level whenever available. it will when you most 1v1 fights. General combo is E -> W -> R-> Ignite (can be activated during ult). Careful with this, you will not be able to do anything other than ignite while it is active. trapping an enemy in null zone with it will do heavy damage. in team fights use it on whoever is giving your team the most trouble.
I use Ignite and Flash.
Ignite can be used along with malefic visions to make sure someone who is running will die and can be activated during your ult (which is when i ussually use it) which often results in them dying before the ult ends.
Flash allows you to get away and can be used to set up your ult combos.
Ghost is good too. Performs similar functions to flash with lower cooldown. Also allows you to chase down your enemies. I simply like flash because i find it better for setting up your kills in center lane during early game.
Teleport is decent. This build has alot of sustain so I don't think its that necessary if you plan on using it to simply get back in your lane. Use it if you want to support other lanes better.
Exhaust is okay. Malz has no slow/stun other than ult which also self stuns so this isn't terrible. can be used to chase or run away along with greatly weakening those pesky AD carries. I simply like other spells better on Malz
Ive seen the occasional person with clarity or heal. They are pretty much a waste. Once you get your catalyst for RoA you should have plenty of sustain. Other abilities will serve you better.
Thats it. Good Luck and have fun. Please comment with your input.