Abilities of Vex
Spell skill priority is an important winning factor for Vex. Understanding the abilities of Vex in League of Legends is another. Below you can find all the relevant information on Vex abilities. In order for item builds you should check the build for Vex.
Passive: Doom 'n Gloom
Vex periodically becomes empowered, causing her next basic Ability to fear enemies and interrupt dashes. Whenever a nearby enemy dashes, Vex applies a mark that can be consumed for bonus damage that also reduces the cooldown of her empowered state.
Mistral Bolt
Launch a damaging missile that accelerates mid-flight.
Vex launches a wave of mist that deals qdamagecalc magic damage. After a delay, the wave becomes smaller and faster.
Consumes Gloom on enemies hit.
Personal Space
Gain a shield and damage nearby enemies.
Vex gains shieldcalc Shield for shieldduration seconds and emits a shockwave that deals wdamagecalc magic damage.
Consumes Gloom on enemies hit.
Looming Darkness
Summon a damaging and slowing zone that applies Gloom to enemies.
Vex commands Shadow to fly to a location, increasing in size as it travels. Upon arriving, it deals edamagecalc magic damage and Slows by slowamount*100% for slowduration seconds.
Killing an enemy with this ability reduces Doom'n Gloom's Cooldown by gloomcdnonchamptooltip*100%.
Applies Gloom to enemies hit.
Shadow Surge
Fire a missile that marks an enemy champion. Recast to dash to them and deal damage.
Shadow excitedly surges forward, dealing spell.vexr:rdamagecalc magic damage and marking the first enemy champion hit for 4 seconds.
Recast: Dash to the marked champion, dealing spell.vexr:recastdamagecalc magic damage on arrival.
If the marked champion dies within spell.vexr:takedownwindow seconds of taking damage from this Ability, its Cooldown is temporarily reset.
FAQ on Vex
What do you max first on Vex?
Most Vex pros max out 
Mistral Bolt first.