Unholy Bolt
This build focuses on Unholy Bolt as its primary core skill.  With proper Mana management through Damnation, items, and Harmonic Form, you should be able to maintain Mana such that using your weapon’s Basic Attack is not absolutely required when the build is complete.  You will still need it while leveling this build.

Radiant Blast
While using the Brilliant Herald legendarium passive, turning it into a very powerful cooldown.  Unholy Bolts will effectively clear out areas quickly, but you’ll need some stronger tools for elites and bosses.  This build raises the Light bar much less often than the Dark bar, so Harmonic Form doesn’t trigger as often, but you’ll still be able to build it up over time.  Substitute Holy Fury into the build if you want more frequent Harmonic Form usage.

Entropy
Similar to Radiant Blast, combining a high-level Entropy with the Molten Reach legendarium passive turns it into an extremely powerful cooldown skill.  Between the two, you’ll have a lot of on-demand burst damage when you need it most.

Conjur Electrode
With a max level Conjur Electrode in the build, you’ll have reliable access to a potent Cast Speed modifier, increasing the effectiveness of Unholy Bolt by a large margin.  

Lightning Barrier
Since Lightning Barrier has built-in synergy with Shock Bolts, it makes sense to include in the build as a utility support skill.  It’ll come in handy when surrounded.

Thousand-Volt Burst
1-point in this skill is enough for keeping the powerful Cast Speed buff in reserve for tough fights.  Invest further if desired, but the Cast Speed bonus is what this build craves the most.

Light Spear
Adds a second burst damage tool that doubles as a further Light Bar generator.

Damnation
As fast as you’ll be casting Unholy Bolts in groups thanks to your Cast Speed modifiers, you’ll want to bring Damnation along to keep your mana topped up.  Without it, you’ll find yourself drained more frequently.

Shadow Step
As with most builds, it is recommended to bring along a mobility skill. Luminous Run can be substituted in instead of Shadow Step if you prefer to sacrifice a little mobility in exchange for raising the Light Bar quicker.

Tingling Sensation
Pair this passive with a Shocking weapon to conjur almost as many Shock bolts as you do Unholy Bolts, dispatching groups of enemies with all sorts of magic projectiles.

Shocking Display
This build utilizes Shock bolts in a number of ways, so to maximize synergy, you’ll want these passives to increase the potency of your Shocked debuff, Lightning Barrier, and Conjur Electrode.

Lightning Strike
To top off this build, a point or two into Lightning Strikes will at some nice additional damage to shocked enemies.

Soul Flask
Mandatory to the build, as it greatly increases the effective area of Unholy Bolt.  With Cast Speed from Electrode, Soul Flask, and max level Unholy Bolt, you’ll coat the battlefield in shadowy bullets.

Molten Reach
As mentioned in the Core Skills, this slotted into the Legendarium will create the burst damage needed for tough fights.

Brilliant Herald
As with Molten Reach, the Brilliant Herald will help create additional damage providing for an even more robust build