This is my first guide so keep that in mind while reading it, help me improve it instead of flaming on me for missing something!

Malzahar has very high damage output even at low AP, so this build is based around survival rather than stacking ap. I've found that Malzahar is very often focused in teamfights, which is why I started using 'tank' items instead.

Pros:
Very resillient compared to other builds
Damage output is still very high
Great farmer
Can tank towers and teamfights

Cons:
Doesn't use his abilities to their full potential
Lacks taunt so he can't really be considered a tank

Ghost: I prefer this one over Flash, lets you chase those annoying runners.
Ignite: Combined with Malefic Visions, Nether Grasp and Null Zone. Don't forget that it can be cast while channeling Nether Grasp! Haven't confirmed this but I've heard that it counts towards summoning your voidling.
Flash: Helps towerdiving early and mid game, also great when fighting in jungle to engage or escape.
Cleanse: Helps escaping but most skilled players will cc you while channeling your ulti, so I wouldn't recommend this.
Clarity/Heal: Equally useless, play defensively and you won't need them at all.
Exhaust: Useful in teamfights on a physical carry but that's what you have your ulti for so I wouldn't use it. Depends on your preferences.

Mark of Insight: Standard caster rune.
Seal of Clarity: Much needed manaregen early/midgame.
Glyph of Force: Helps increasing the damage of Malefic Visions while lvling.
Quintessence of Potency: I prefer this one over Quintessence of Insight due to the lower endgame AP of this build.

Offense: Standard caster build. Burning Embers for that little extra when Ignite is on cooldown
Defense: Strength of Spirit helps staying in lane longer without recalling.
Utility: Haste, 5% experience, manaregen all help your laning and ganking early game.

I choose to start with boots of speed, 2 healthpots and a manapot. The extra speed will help harass the enemy chamions and using Malefic Visions helps keep your manapool full.

Depending on how good you are with Malzahar getting Mejai's Soulstealer or Rabadon's Deathcap will make a huge difference. I prefer Soulstealer for the extra 15% cooldown reduction fully stacked, if you're not sure you can stack it I'd go for Rabadon's Deathcap instead. They both give almost the same AP but Deathcap is more expensive.

Banshee's Veil: arguably the best defensive item ingame, especially vs those annoying Blitzcranks and Urgots out there. Core item in all my builds.

Rod of Ages: Extra hp/mp, extra damage and surviability in one item. Could be replaced with Rylai's Crystal Scepter if you prefer the slow but all of Malzahar's abilities are aoe or dots.

Leviathan: Again depening on how skilled you are with Malzahar this item could be replaced with the more expensive Warmog's Armor. 15% damagereducion vs 400 extra hp.

Sunfire Cape: Against mixed AD/AP teams for the extra hp and armor. Could be replaced with Force of Nature against heavy AP teams.

Harass with Call of the Void, Malefic visions and when they're low enough you engage with another Malefic Vision, Null Void and Nether Grasp for the kill.

Call of the Void and Null Void can deal devastating damage in teamfights, Nether Grasp on their damage dealers or cc champions further increases your usefulness in teamfights.

While the damage output is lower than your standard Malzahar build your survivability is really high. Tank Malzahar still retains alot of his damage output but your enemies will regret focusing you giving the rest of your team time to kill them. I went solo vs Irelia, Katarina and Sona in their base killing all 3. My last game with this build ended with 26/2/13.

I realize that most people are sceptical to builds like this but I can assure you, your damage output is still comparable to other casters stacking ap.

I would appreciate comments and recommendations but plz don't downvote before trying.