Our build is focused around the Lightning Blast skill, but we use it in a fairly unique way. First, we take the Innate Conduit node to make it so we can cast lightning blast while we're out of mana. Then, we take Insidious Conduction to turn it into a channeled skill. This allows us to channel indefinitely against a single target. Once we unlock this, around the time we get our mastery, we can use channeled lightning blast to be a great single target DPS and just focus on dodging big abilities. Then to turn the skill into a real strong one, we go for Halo Effect. This makes it so the first hit of every single lightning blast you do while channeling adds a Spark Nova. This gives our channeled blasts good AOE clear. Thanks to the way Lightning Blast targets, we can basically wave our cursor in the general vicinity of the mobs and everything will die. Finally, we get Lightning Attunement to ensure that we have permanent uptime on Lightning Aegis.
Since we're standing still most of the time we do damage, we want to use our other skills to support this. We need to work around the fact that we're always out of mana, so we use Teleport's Mana Tunnel node to make the next spell we cast refund it's cost. This alone allows us to cast any of our supporting skills immediately after teleporting. Early on, teleport will cost enough mana that you might drop back into the negative and have to wait a moment to cast them, but as you stack more intelligence and/or mana regeneration affixes on your gear, it will reduce the cost enough that the synergy feels good. Once you get your third mastery for Runic Invocation, we get to have some fun. Using the Attuned Approach node, Runic Invocation will refund a portion of its mana, which stacks with Mana Tunnel to make us refund more than 100% of Runic Invocation's cost. That little mana bump allows us to then cast Flame Ward or Glyph of Dominion (or both) before going back to channeling Lightning Blast.
Once you have all these pieces together, you can Teleport into position, cast Runic Invocation (Ball Lightning), triggering Brand of Deception on rare/boss enemies, drop Glyph of Dominion for the defenses, pop Flame Ward for additional defenses if necessary, then channel Lightning Blast until everything nearby is dead. Once teleport is back off cooldown, we can stop channeling for a moment or two, teleport to a new location and resume the channeling.
Other Mechanics
Because we are channeling to 0 mana, this removes the need for us to stack any amount of +mana. Cast speed only affects the initial start of channeling, and the amount we get from passives and skill trees is enough to make things feel good. This means we can use our gear affixes to focus almost entirely on other damage boosting things. Increased damage, crit chance, crit multiplier, penetration and shred are all great affixes for us.
To make it so our mana regenerates fast enough to be able to cast teleport immediately after we stop channeling, I find that a PrefixMana Regeneration prefix on your belt is enough, but if you feel like you need more it should be fine to toss on your rings as well.
Between Prismatic Gaze and Crystal Skull, our base crit for both Lightning Blast and Spark Nova should be in the 13-15 range, making Calculated Destruction cover a large chunk of our necessary crit chance.
Defenses
Because of the style of this build, we're actually locked out of some of the common defenses that many mage builds use; this also contributes to the build feeling a lot different than other builds. Since we have 0 mana most of the time, we can't use PrefixMana Spent Gained as Ward or PrefixDamage Dealt to Mana Before Health as defenses, and because we're channeling for our damage, we can't use Twisted Heart of Uhkeiros to give us ward based on our casting. This means we have to focus on some other ways to generate ward as our primary defenses.
PrefixPenetration with Lightning Invocations gives us exactly what we need. We're using all lightning skills, which means we're constantly at 3 Gon runes. A level 1 version of this prefix on your chest and helmet will give you a whopping 90 ward per second, plus you'll be going for the Inscribed Patterns node on your runic invocation, giving you another 36. With 126 ward/second at the start of Act 3, you'll have enough passive ward to carry you through most of the campaign. By stacking intelligence and other sources of ward, you'll be able to easily walk through the campaign and regular monoliths with little to no danger.
For our resistances, we can make use of the SuffixAll Resistances While Channelling affix, which basically solves all of our resistance problems as long as we're channeling. I'd recommend being close to capped resistances without channeling though, just in case you take some hits while resetting the skill cycle. Overcapping our resistances is very strong because we're using Frostbite Shackles for an insane amount of bonus ward retention (especially if you have double Liath's Signet equipped), and on top of that we get a lot of ward per second from Charged Reflections as well. If you want to make it even sillier, you can swap Prismatic Gaze for Boneclamor Barbute, which will give you a lot more armor and even more ward/sec from your hugely overcapped necrotic resistance.
Channeling also affords us the ability to use Runic Fortress and Grand Patience of Herkir, which is a ton of flat armor while we're channeling. By stacking that and armor affixes wherever we can, we can get some significant damage reduction going, plus the bonus ward when we channel from Runic Fortress.
Since we're standing still most of the time, we have a tendency to take a lot of hits. Telf'un's Mirage gives us a 15% dodge chance while channeling by itself, and if you can get some additional flat dodge on your rings (which can't have armor suffixes), you can get to 20-25% dodge, which makes it not nearly so bad.
Another benefit of building Teleport with the free spell from Mana Tunnel is that we get to allocate Rock Phase for permanent stun immunity.
