Runemaster is one of the most complicated masteries to play in Last Epoch. This specific path that all Mages take requires a more piano-style gameplay, compared to other simpler subclasses. Regardless, a high-skill curve generates pretty high-value results as well, as Runemasters excel at melting enemies in the highest corruptions.
This article goes over an endgame build for Runemaster that takes the very first ability given to Mages in the game and makes it a lethal force against large mob packs, alongside Uber bosses as well.
Skill setup for Runemaster Lightning Blast build in Last Epoch S3
In this Runemaster build, we are going to utilize the Lightning Blast skill as the main source of damage, alongside Runic Invocation for high Ward generation. The Runic Invocation is also going to turn into your movement skill later on, alongside other abilities such as Runebolt, Frost Wall, and Flame Ward.
In addition, those three skills will be placed on the first three slots of the hotbar, and the Runic Invocation's tree, Immutable Order, which will trigger a passive called Reowyn's Frostguard for the Ward Generation.

Lightning Blast:
Your main damage skill in the build. Start with Frontloaded, followed by Cloud Answer, and then Hypercharge. Next, get Moral Capacitor for more damage with Spark Charges, Chain Lightning for more chains, and Convergence for increased damage on single targets.

Lastly, get Arcing Power, and specialize until Halo Effect on the left.
Runic Invocation:
Get the Immutable Order node to get fixed runes with Lightning Blast casting. In this case, you should be getting Cold-Fire-Cold from Runebolt, Frost Wall, and Flame Ward. We will be changing Runebolt to a Cold skill, Frost Wall to Fire, and Flame Ward to Cold.
Hence, it is essential to put Runebolt>Frost Wall>Flame Ward in that order on the hotbar from left to right.

Get Enigma node to turn Runic Invocation into a movement skill. For the remaining tree, follow the image given above.
Runebolt:
Convert Runebolt into a Cold skill by taking Frost Spikes and Ice Shard. Next, take Arcane Restoration for a small utility, as you can get your Mana back by casting it on enemies.

For the rest, follow the tree given above.
Convert Frost Wall into a Fire skill by taking Brand the Invaders, and Flame Ward into a Cold skill by taking Frost Ward.


How to play Lightning Blast Runemaster in Last Epoch Season 3: Skill rotation explained
The gameplay loop starts with you casting Runebolt once and spamming Lightning Blast. This will turn the three runes into Cold>Fire>Cold for Runic Invocation's Immutable Order node, and then cast your Runic Invocation for getting increased Wards.
Occasionally, cast Runebolt to get your full Mana back, and then cast Frost Wall on bosses for increased damage.
Best endgame passive tree builds for Lightning Blast Runemaster in Last Epoch Season 3
Here is the passive tree for Runemaster:

Take Arcane Warden in the Spellblade tree, alongside Arcane Momentum, Calculation Destruction, Essence of Celerity, and Rift Bolt in the Sorcerer tree.
Last Epoch Endgame Lightning Blast Runemaster itemization guide

Here is a list of items you must have for your Lightning Blast build:
- Mad Alchemist's Ladle Wand with increased spell critical chance Legendary.
- Fragment of the Enigma Catalyst with spell critical multiplier and chance Legendary.
- Vilatria Storm Crown set item Helmet.
- Static Shell Body Armor with Intelligence Legendary.
- Twisted Heart of Uhkeiros Relic with Intelligence Legendary.
- Grasp of the Blood Mage Gloves with Intelligence Legendary.
- Foot of the Mountain Boots with Intelligence and Health Legendary.
- Orian's Descent Belt with Health and increased Health Legendary.
- Legends Entwined Primordial Ring to complete the set bonus of the Helmet, with Intellogence Legendary.
- Opal Ring with T7 Intelligence and Spell Damage.
- Idols with your preferred resistances.
Best Blessings to use for Lightning Blast Runemaster in Last Epoch Season 3
Here are the recommended Blessings from Monoliths:
- Critical Strike Multiplier: The Black Sun.
- All Resistances: Reign of Dragons.
- Flat Armor: Spirits of Fire.
- Increased Armor: Age of Winter.
- Chance to Shred Lightning Resistance: Ending the Storm.
Follow more on Last Epoch and Season 3:
- All minion improvements in Season 3
- All new Lich and Necromancer skills (and reworks)
- Primal Hunt mechanic: Rift Beasts, Evolution, and new Runes explained