Skills for an Inferno hero.

Why wouldn't this chaos spell be effective? Against, say, Light Elf or Human units, a Fireball spell with a Warlock targeting Paladins/Archangels/Dragons, etc., can be very helpful.

Without artifacts boosting his spellcasting, his damage will be weak. I prefer Darkness. As for Gate...it depends on the situation. If there's a chance to hit some Paladins or Riders, then forget about Gate; an attack is more important in these cases.