Hello, I made an Archmage Frost Bomb of Forthcoming build this league I used to successfully clear all Ubers and after being messaged in game by a fellow exile named "Dancingblast" looking for tips on how to build it I figured as I am one of only two people on PoE Ninja playing this skill, once I made sure the build was capable of clearing all Ubers that I would make a reddit post about the build as my small contribution to the collective knowledge of the PoE community. I would like to preface this with I am not good, this is the first league I have ever killed Ubers after 1000 hours (partly because I am a "I want to make my own build" type of player) I would bet money there is a better way to build this but this is what I could think of. If you are gonna play this you have to at minimum read the "Actually Interesting Mana Regen Tech" part its pretty important.

Actual Build Guide Starts Here - PoB at the bottom aswell as a kinda TL;DR
Gonna give some general ratings for the build so you can see if its what your looking for
Price: 5/10- Idk 30-50 div I wasn't counting
Mapping: 5/10 - Pretty good clear speed but loot drops behind you and map mods can be really bad
Bossing: 9/10 - Trivializes all bosses that aren't Uber and can still kill Ubers if you dodge stuff
Tank: 8/10 - to match the 80% of the time you have Arcane Cloak

Frost Bomb - So the idea behind this build is I am taking Archmage's large flat damage and then scaling it with Frost Bomb of Forthcoming's large More Damage Multiplier that it gains from scaling duration and then with some Area of Effect, Spell Echo, and Spell Cascade we get anywhere between 4-12 Frost Bomb overlaps (or 8 on average which is what's in both PoBs). Then we get a lot of Increased Cooldown Recovery to get the cooldown of Frost Bomb from 4 seconds to 2.221 almost doubling DPS.

Arcane Cloak - Because we are Archmage we obviously use Arcane Cloak which also scales extremely well with Duration and Cooldown ending up with us having 81% uptime on Arcane Cloak. Because of that I think this is one of the best builds to run Veteran's Awareness in making us extremely tanky when its up. The only problem is when its down you take 20% increased physical damage but this is honestly not that big of a problem. With the defences we get I barely die in maps and so you are basically just gambling on/playing around things hitting you with something actually capable of killing you in the 81% of the time when its up.

Actually Interesting Mana Regen Tech - I saw a video of a guy playing Cremation Archmage (https://youtu.be/5Broti2dPdE) and he was using the "Regenerate 5% of mana over 2 seconds when you consume a corpse" suffix on the new charms with Disciple of Kitava to get insane mana recovery and I was inspired to do the same in this build. Its great and easy to get while mapping but for bosses it gets more complicated, so we use Golems with Infernal Legion support + Liege of the Primordial from the Elementalist + Heartbound loop + CWDT with Desecrate to create a cheap CWDT loop consistently dropping corpses on the ground for us to eat giving us like 7K mana regen per second after scaling which feels really nice. It is a little clunky sometimes though like if your moving around a lot for a boss like Sirus, you move away from your corpses have no mana regen and have to wait for the golems to die and trigger CWDT again. When we have Righteous Fire active and cant eat a corpse sometimes you can soft lock where you have no mana and no regen because of Righteous Fire so you cant spawn corpses at which point your options are either find a corpse to eat on the ground, use a portal scroll to go back to hideout, or die. This has only happened to me once though.

Gem Swap - This build has 1 gem swap and its swapping Increased Duration for Less Duration in the main 6Link while mapping because waiting 8 seconds for a Frost Bomb to go off is just not reasonable and we have enough damage to 1 anything in a map with less duration on including map bosses anyways. Even Guardians just fall over with this build it does so much damage. The only time I swap Increased duration in is for Pinnacle/Uber Bosses or Maven Invitations.

What To Farm With This Build - I really think you can do a lot of stuff with this build it has pretty nice clear the only problem with mapping is that because the skill has a duration when stuff drops it drops behind you so looting can be annoying. But I highly recommend just like Boss Rushing any of the guardians with Essence and Rogue Stashes for extra money, doesn't matter which conqueror, you will one shot all of them just pick your favorite, or I just kill all of them in rotation because its more fun to fight different ones and then sell the Maven's writs they are worth like 2.5 div at the time of making this and I bulk sell the contracts and essence on TFT. here is a very good video (https://youtu.be/qX0b6x1CFzk) but I run it slightly differently because I hate 7th gate so I will post my no investment atlas tree at the bottom (you will still need to buy guardian maps so its not like 0 investment I guess).

Map Mods - Also worth mentioning is map mods are a real problem with this build. No regen, Reduced Cooldown Recovery Rate, Reduced Duration of Buffs, and Elemental Reflect are all quite bad but if you are doing the boss rushing strat you just scour every map anyways so it never really matters other than when you are in the Maven Invitation but I have yet to ever lose one even when they had these mods. The only complete brick is really No Regen or Reflect and we can fix reflect by having a tech No Reflected Elemental Damage Taken charm to swap in if needed. Regen is just a brick though really.

Kinda TL;DR - Other than the mana thing the build is really not that crazy and you can just buy the stuff in the PoB if your interested in trying it and it should just work. I would recommend using a leveling build and starting this build around like level 70-80 as frost bomb will just not do any damage or feel good at all until you get some levels. I will say thought the tree is pretty optimized for my setup so unless you are taking this foundation and building it your own way I would say just don't mess with the tree too much.

Honestly I am kind of out of my depths here I am much better at making builds that don't work so I am not really sure how to make a guide but I hope I gave enough information so that people can play it if they choose without too many problems.

Some gameplay - Used outplayed to record, you can watch the videos in browser.
Conqueror Map using Less Duration - https://outplayed.tv/media/k31ZoW
Elderslayers Invitation using Increased Duration (rolled to 70% quant and then corrupted into unidentified) - https://outplayed.tv/media/87w3n2
Also in the Invitation you see me get low but it honestly shows how the defence is pretty good. I used Vaal Righteous Fire right as Warlord hit me with phys damage while I didn't have arcane cloak up and I still lived.
The PoB I made for myself to follow - https://pobb.in/IE4NagN7GTSG
My actual character - https://pobb.in/IE4NagN7GTSG

GL I hope its not trash :D