This build aims to spam lightning surge as much as possible.

You can do so by becoming transcendent and running arcane needle for three melee charges. I highly recommend area denial grenade launchers to gain transcendence energy fast. Lost Signal with auto-loading holster is great for darkness, and Psychopomp with rolling storm is great for light energy.

Rolling storm is also going to grant you bolt charge on every kill. Since these grenade launchers do damage over time, you can quickly stack up to max bolt charge. Getting bolt charge stacks will also grant melee energy, so you can use your lightning surge more often. Lightning surge will also grant bolt charge stacks per enemy hit.

With feed the void, you will permanently have devour to heal and grant grenade energy on every kill. The grenade you want to run is coldsnap to freeze targets. You can take advantage of this with facet of courage to let your lightning surge do more damage to darkness debuffed targets. Then, with devour, you can spam these all the time.

The heal from devour is also very strong for survivability. We can pair this with facet of protection for added damage reduction. Then, with facet of purpose, we will be granted woven mail on orb pick up, which is more damage reduction. Then stack on the passive damage reduction that amplified gives now, alongside the transcendence one, and you are pretty much unkillable.

To deal with champions, you have facet of dawn to grant radiant when you get a melee hit. Radiant will let your weapons deal with barrier champions. Going for that melee with lightning surge will also apply jolt. Jolt will stun overload champions. Finally, with your coldsnap and transcendence grenades, you can freeze enemies. The shatter from this will stun unstoppable champions. Note that your transcendence grenade can also stun overloads due to its slow and suppression. With all that being said, you won't need any artifact perks with this build.

For your class item, you are looking for synthoceps and any supporting perk. I personally like pairing it with assassin to go invisible on every melee and finisher kill. Pairing that with all our damage reduction and healing, you are again unkillable.

Important armor mods to run are three heavy handed mods, so you can make orbs on every melee kill. Then, things like invigoration to grant melee energy on orb pick-up means using your melee gives melee energy. Pairing that with facet of balance and bolt charge from earlier, using your melee grants a ton of energy back. Plus, all the orbs will grant armor charge and woven mail. You can take advantage of that with special finisher to make ammo for your double special setup. Paring that with proximity ward, you will get an overshield while finishing an enemy, and then with assassin, you will go invisible after.

With all of that you can get one of the strongest Warlock builds in the game!