This is a malzahar build that will be briefly explained because the best way to build is to free play agaist bots until the build suits you, however i will go over the very basics

first of malazahar in this build is a MID characher try never to go top or bot

Pros
High cooldown reduction for ult
lots of mana and health
high ap

Cons
No escape tatic
In the beginning Squishy

All runes are cooldown reductions because malzahars ult does a lot of damage(if used correctly) but has a longer countdown so cooldown reduction will be important

You need exp and cool down reductions so level up utility 1st then move on to attack masteries

Malazahar has almost no escape tatic so I build him with cooldown reductions so that his ult will be ready to supress a champion and hopefuly scare the champion away or lowers health so the champion becomes easier to kill

Malefic visions is the mana generator of this build so it gets upgraded fully 1st

Call of the Void is chosen 1st because it can be use to check bushes and is continuely upgraded because the attack is a nuke(basicly keep useing this to take their health down to halfway before any combos

Nullzone is only to be used if A) for some reason your with a champion with a stun or B) right before your ult and then use your ult to freeze them in your trap

NetherGrasp is only to be used if nullzone and malific visions is not cooling down use them before

Voidlings are nice pets to have but they are stupid and only attack targets with Malefic Visions so wait until the vodling gets big before casting on a campion, i dont try to spam spells to get a voidling but they come as a nice surprise

Ignite i use with cominations

Teleport i use when i have low heath so i go back to base and teleport back to mid so my lane is never without a campion

When half health(opponet)

use Malefic Visions on a minon next to a campion
then use Call of the Void to silence( Malefic Visions should hop on the campion)
Use Nullzune and "Catch" the champion in it with NetherGrasp