Zhask, The Planes dominator.

How do one, use this mage?

Easy. Zhask is really a powerful hero when used perfectly. The best way to use Zhask in early games is ambush. Why? Hiding your Nightmare spawn on the bushes makes the enemy unaware of its presence, and when the enemy walks in range, they will have near to no time to react, as The spawn stuns the enemy and you can finish them. On later games, especially on clashes, spawn the Nightmarish spawn on places many wont know its coming, especially when an Argus hooks his way into the clash. The spawn, with ult, can tank Argus' blows while you safetly lazer him from behind. The spawn can also be used to push,dont just use your ult at the turret, thats wasting, unless its necessary. The death explosion can also kill, so be sure that if you're almost no HP, run towards the enemy heroes like a kamikaze bomb,Put a Nightmarish spawn and ult to double the damage,flicker or sprint, then boom! Let your teammates finish the remaining enemies.

As for the build, use magical penetration, spell vamp, and feather of heaven, and lighting thrucheon. Put blood wings too! Then Immortality

With Zhask, you can dominate the land of Dawn, as the PLANES DOMINATOR.

Make The enemy Argus eat dirt!

Enjoy using Zhask while dominating the world!

Use Flicker, Sprint or Inspire as spell, and as I always say, Practice at custom or VS AI