Every league I post an inquis homebrew guide here, and while this certainly doesn't reach the damage : durability : cost ratio of last league I'm still quite happy with it. While not likely to make it through ubers, I've wanted to play glacial cascade forever and I'm really glad I finally got a build with it up an running. I posted a rougher version of this build a few weeks ago looking for some help, now I am back with a more concrete guide.

https://pobb.in/4fPvNusdtylS

30M burst dps, very good vs phys and fine vs ele with glancing blows capped block and % life on block shield as well as pious path regen. Playstyle may be a little spiky for some, but even without any of the conditionals up it feels smooth as far as slefcasters go.

EDIT: PoB for ubers (fingers of frost added) https://pobb.in/Zto3tpGfm2P2 - I killed uber shaper first try, the damage is definitely there but the defenses are simply not good enough for those fights.

You can achieve 20m dps and reasonable recovery / defense at maybe 25div on this setup, though early league that could be more as the boots could be quite expensive. I paid 5 div for the shield, a few for the weapon, and everything else is cheapish as far as gear. Jewels aren't terrible either, fanat is 1-2 div for the set and although str/int split personalities went through the roof at some point that can easily be replaced with something else. Most of the cost is in gems, which are again entirely workable without the woke or +lvl versions. Bossing is incredibly efficient, mapping is fine with good AoE and great damage but no offscreening or prolif/explodey. As is, the build does NOT hold up in simu past wave 25ish, and lacks some comfort options like corrupted blood immunity (comfort because cb does NOT kill it through regen and pdr) and chill / alt ailment defenses / high movespeed.

First, let me discuss Heatshiver. This item gives 130% more damage you can satisfy its conditions. That's ABSURD, even better than replica frostbreath on a replica alberon's char. Unfortunately, those conditions are to max chill and then freeze the target, meaning bossing and esp ubers are going to be incredibly difficult to actually keep that dps on permanently. It's also fire damage, so either you'd need to convert your cold damage to fire and still have a way to chill / freeze, OR you're dealing 2 elements of damage. If you can solve those though, more than doubled dps is a hell of a payoff. From what I've theorycrafted we want either inquis or witch (explained at the end).

The core synergy package is somewhat standard, and is stuff I use/abuse on a LOT of inquis builds because it's just so efficient.

-Inq ignores resists to avoid split ele downside and free up a curse

-Pious path + corrupted soul + RF enables a large more spell dmg multiplier while still giving a huge amount of net regen

-Skin of the lords + corrupted soul + melding (notable) gives a ton of ES and non-negligible armor, making one of the best offensive body armors also defensively sound. Skin also lets us hit gem level 30 without shield or amulet.

-Petrified blood enables a TON. It lets us reserve max vitality, clarity, and defiance banner without using mana while enabling pain attunement. It also "doubles" our max hp for % based recovery effects, esp the % life on block synth shield and pious path regen.

-The other novel choice here is fanaticism. Activated by shield charging around, it lets us nuke bosses HARD when they enter a new phase or after we dodge a major mechanic. It also enables a divine blessing aura as well as skating by on what would otherwise be questionable mana regen. And because of the mechanics of glacial cascade, it gives us extra overlap for easier multihits, resulting in more consistent dps and even higher damage than shown by PoB.

All of that will get you a passable character, best with extra flat pdr and any maxres you can get (shield with both advised). But we still have an ailment issue and not incredible damage. Freeze is based on hit damage, and our average hit is nowhere near being enough to reliably freeze. Since ailment effect doesn't scale freeze either, the best play is to make the damage spikier. GC is actually great for freezing, as its large burst is a single massive hit that divergent makes even bigger. Woke spell echo gives 20% double damage chance, and the new combo of ralakesh's impatience + arn's anguish gives 15% triple damage chance. Now if we hit HALF the boss's ailment threshold, we get a freeze 35% of the time! At 7+ casts per second, that's plenty. It's also 50% more damage overall when averaged out, combined with heatshiver's 130% this 3 unique item combo gives us a 245% more damage multiplier and then perma frenzy / power charges.

Important note: PoB uses average damage for ailment calcs. Things with wide damage ranges or double/triple damage chance will inflict higher damage on a lot of hits than PoB expects and thus get bigger ailments, so using things with really wide ranges (ie ruthless + multistrike) yields higher than usual ailments with sufficient hit rate. Cull has the opposite effect though, raising calculated average damage per hit without actually raising single hit damage.

Bonus Notes, Ideas, Variations, Theorycrafts:

-Frost shield and diamond flask are redundant, it's a matter of uptime to run both. For ubers bottled faith would likely be the play to try and nuke even harder during the fanat window.

-The Eternal Struggle is really good. It's hard to overstate how good it is, especially with skin since I can hit gem level 30 without any levels on ammy / shield. Cull is 18% more damage, the attributes are actually huge as a mini-astramentis, and aura effect + recovery rate + global defenses is a fantastic batch of extra stats to grab but things like block or crit multi are also huge.

-With one more socket freed up (and dropping the inspiration on divine blessing) I could run bonechill + vortex for a "free" extra link, but the spacing would be odd with GC's fixed distance. Bonechill could probably be subbed out regardless.

-Heatshiver procs trinity naturally if you can freeze. A witch(or ascendant ele) build using double exposure, ie gloves for cold and medium cluster notable for fire, then mastermind of discord could theoretically pen resists into the negative with VERY little effort. Mastermind on occultist strikes me as the best way to do this, enabling power chage synergy, ele weak + assassin's mark, and extra free exposure / free freezes. I could see this having some legs in a CoC setup, but I've never built one to know how to tweak that stuff in. Plus using CoC will lose you damage per hit, so perhaps that won't work after all.

-Either frostbolt or freezing pulse is probably just the best spell for heatshiver with minimum effort, the damage per hit is crazy.

-Don't roll more life on invites unless you know you freeze through it, the difference between "freeze on highroll triple dmg proc" and "freeze on any double/triple and some single" is huge for your ability to consistently nuke bosses.

-Unnatural instinct is like 15% more dps if you can afford it and have at least two more dexterity on gear than I do.

Videos - you can see the difference in burst and the importance of proper positioning here, some of these I mess up and others like the 2nd phase of elder I position well and get a huge damage window out.

Elder: https://youtu.be/N2D1fkjnMoI

Guardians: https://youtu.be/ARSURjYVjIM

Formed: https://youtu.be/pCHRfZ1k8Mk

Sirus: https://youtu.be/9_wk5JPRSwg

Should swap in a cb jewel for this, I didn't because I assumed he wouldn't shoot a die beam

Eater: https://youtu.be/jimHRUex9xI

I think I can call it done and move on to darktide / the new gunfire reborn content / theorycrafting the witch/scion version til 3.20. I do have another 20 div to throw at it but honestly don't see the line where I make meaningful upgrades with that. UPDATE: With fingers of frost we can freeze ubers and the damage is actually pretty viable. Unfortunately, without suppress or massive maxres our ele defenses are way too low. I was able to beat Uber Shaper first try with a flawless last phase after taking some early deaths to get into the rhythm, but Maven and even a white EoW pretty much two shot me during molten shell's cooldown with their basic attacks. I can avoid shaper balls and bullet hell, maven has way too much going on in that arena to be perfect though. Spell block is just not a meaningful defensive layer vs bosses on its own, even with recovery on block. Which is a shame, because it basically means left side builds either need full suppress gear OR some melding maxres shenanigans. I do hope GGG will look into this, suppress was busted but this is pretty rough too. While there's a path to converting this build to melding + aegis + purity of ice, that loses the whole novelty and affordability of what I've got here and suddenly just becomes the same cold reap I made last league with a new helm and no suppress. Dawnbreaker + purity of fire + temp by war is an option too, but very hard to get enough cold/light res to do that and this build cant use sublime purity of fire without turning into a shittier version of fire reap chief.

EDIT: Credit to u/quantum_hacker and u/cratonz for pointing out that I had missed the fingers of frost wheel adding 50% increased freeze duration and making ubers freezable. Seems I'm going back to farming up some boss invites to run them uber'd and see if I can pull the mechanics off on a build that has to actually respect them, will edit in videos if I win any.