Cast on Freeze II: Return of Cast on Freeze

I started out with a mana/int/manareg scepter and es/mana/manareg/int focus and that worked alright until late red maps. I kept using Elemental Invocation to instant delete rare mobs and bosses but eventually my comets stopped oneshotting mobs in maps with extra hp/res/es.

At that point I got lucky and bought a fairly cheap +60 spirit amulet (alternatively you can of course get a chest, but those don't really come with +60 spirit for under 500 ex, much less so with 600+ ES). This allowed me to get a wand with +4 to all spell levels, as well as a +2 focus. This more than doubled my damage to the state you can see in the video.

Armour is mostly generic +mana +es +res +int. I didn't figure out that jewels can roll "Gain x% mana on kill" until literally a few hours ago, so I hard-commited to mana regeneration (which kinda works too, but you can run dry in breaches and other extreme density situations). Having nearly 800 mana/sec does help a lot with survivability too, but now that the on-kill tech is in play, survivability while mapping is basically solved for good.

Speaking of jewels, they are what makes CoF actually work again. I have 8 jewels with the "Meta skills gain x% increased energy" affix for a total of about +100%. Most of them also come with "Increased Area of Effect" which makes Frost Wall a ridiculous shotgun ability and Comet clear nicely.

Still not sure what to annoint on my amulet. Before I had the points to just path there I used Mental Toughness, but there are very premium mana regen nodes in that cluster, so I much prefer actually pathing there. Freeing up the pathing nodes towards Pure Power would work, but that annoint is like 250 ex. Wild Storm is also a strong contender, but it also has a pricing issue.

Ascendancy points 1-4 go into arcane surge scaling, 5-8 go wherever you want really. Your lightning damage cannot shock even with the shock ascendancy, so you have to hope the remaining frost portion of your spells do. With +70% chance to shock from the tree Frost Wall applies two stacks pretty reliably. Alternatively literally take the small nodes for +4% elemental resists (kinda good actually), +12% damage and some crit/chill.

Open with Frost bomb (to apply frost exposure for better shock chance), and Conductivity. Lay down Frost Wall x3 on top of the boss. Shoot some sparks to pop the walls, the boss is now frozen. Place a Mana Tempest and hard-cast unleash meteor. Repeat as soon as the diminishing returns on freeze go away.
A full salvo like this does anywhere from 1.5 to 3 million damage depending on how large the boss's hitbox is. This is not a great bossing build, but it isn't impossible.

Spark - Arcane Tempo - Persistence - Pierce - Wildshards - Acceleration

Conductivity - Heightened - Hex Bloom - Focused Curse

Frost Wall - Glaciation - Magnified Effect - Icicle - Spell Cascade

Frost Bomb - Fast Forward - Controlled Destruction - Strip Away - Conduction

Archmage - Lightning Mastery

Comet - Unleash - Elemental Focus - Concentrated Effect - Cold Mastery

Cast on Freeze - Comet - Impetus - Energy Retention - Inspiration - Spell Echo

Mana Tempest - Nothing :^)