Hello, and welcome to my very first guide. I made this build myself and it seems to workout very well. I play malzahar alot and I usually carry my team. I wish i could show you my recent games but im new so hehe :p. well anyways onto the Guide.

For runes I get typical caster runes:
9 Magic Pen marks
9 Mana/lvl seals
9 cooldown glyphs or 9 ap/lvl glyphs

I like to get CotV first so i can get my voidling up to farm/harass.
I max Malefic Visions first as it is a very efficient way of farming.
Next i max Null Zone as it does alot of damage With your Nether Grasp

For summoner spells I choose flash ignite.
The Reason being that Flash is a great escape method and ignite to get the kill if he doesnt die from your combo which happens alot early/mid-game.

Pros: Great farmer, Tons of Damage,has a voidling :P
Cons: Gets focused alot late game, doesn't have any escape methods