AK47 - Cursed Spark Archmage

Focus on getting 4 support slots for Spark and for Orb of Storms asap! You can do that by using 1x Lesser Jeweller's Orb and then gambling with Vaal Orb. It might take some time and eventually you will have to get another set of these abilities as we will need to unlock 5th slot as well, which cannot be done after the gem was corrupted. But 5th slot won't come online for a long time! Unless you are lucky with drops to buy it early.

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We are gonna use Pierce as our support gem of choice on Spark as we are instilling amulet with Harness the Elements with this build and thus it will be our only source of piercing. We will more than make up for it in DPS by playing full Sapphire gems with Cast speed and either Elemental, Lightning or Spell damage modifiers, with Cast speed being one of the best stats for DPS increase on Spark. The insane amount of Cast speed will also let us activate and weave spells much faster, which will in turn give us even MORE Cast speed thanks to Casting Cascade.

Personal recommendation for first 3 support gems on Spark, for a mix of AoE and Single Target DPS, is Arcane Tempo, Persistence and Pierce. In this setup we are instilling Harness the Elements and focusing on Sapphire jewels as we will only have mana as our life and no Energy Shield whatsoever. Thus we are keeping Pierce the whole time. You can also choose to get 5x Emeralds with 20% projectile pierce and thus you could slot in Rising Tempest, but those are really hard to come by and will cost us %mana on kill and thus reducing our sustain. Then we get either Inspiration for better mana sustain or Acceleration for more damage as our 4th slot. With the other one of the two being our 5th. Early on I recommend Inspiration to be used on Mana Tempest with Culling Strike and Premeditation as we won't have enough mana and stats for Archmage to come online. And DPS gem on Spark plus mana conserving gem Mana Tempest will grant you the highest DPS.

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For our Orb of Storms, we want to get Magnified Effect with Conduction and Lightning Exposure asap. I recommend asking in trade or looking online for Uncut Support Gem 3 to unlock Exposure as they go for like 0.01 exalted orb these days and you can get them right at the beginning of the game. Or ... almost. If you cannot get your hands on them, then definitely go for Font of Mana for better mana sustain instead. Which will later become either your 4th slot or 5th slot depending on whether you need extra mana regeneration or whether you just wanna do more DPS through higher exposure. We can also use Overabundance instead of Conduction for more on demand DPS with two orbs active at the same time!

As I previously stated, we are gonna start with Cast on Shock as it is much easier to get rolling and in combination with Voltaic Mark it procs all the time even after the nerf letting us one one shot bosses/priority mobs. Once we have enough stats to start using Archmage, we will remove it

To better sustain mana, we are also using Mana Remnants with Clarity and early and mid levels, before we can sustain Mind Over Matter , we will also use Cannibalism with Vitality (if you can only use one, use cannibalism)

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Once we have enough stats and sustain in our build with items like %mana on kill Jewels, we will remove Mana Remnants and put Cast on Shock back in to further increase our, mostly single target, damage. For that reason, get 170 spirit combined on amulet and chest to be able to also use Clarity on our Archmage.

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Archmage + Lightning Mastery +1 skill from corruption and 20% quality (high risk high reward of corrupting after maxing out quality) is the BIGGEST DPS INCREASE we could ever get as it will exponentially scale with our mana.

This build focuses on curses to get extra survivability ( Enfeeble ) and reduce enemy resistances ( Conductivity ) combined with applying Lightning Exposure using Orb of Storms to make enemies take ungodly amounts of lightning damage with no way to protect themselves against it. Combine this with Scouring Winds that increase the base exposure from 20% to 40% and Overexposure and we are looking at more than -100% lightning resistance on enemies combined!

Our curses also gets further boosted with passives like Master of Hexes, Lingering Whispers, Impending Doom, Fated End and Zone of Control making them extremely potent in our build.

Conductivity will also keep spreading on enemies thanks to Hex Bloom and thus we won't have to keep recasting it while chain pulling or in big pulls in general.

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Chaos Inoculation is not recommended before you have at least 3000 mana, maxed out elemental resistances and a few jewels with %2 mana per kill to have infinite mana pool = infinite life.