DISCLAIMER: This isn't meant to be a guide but a proof of concept. While I did play this character straight from day 1 of the league, I don't really recommend it early because it's a bit clunky before Divergent Berserk and Lethal Pride appeared on trade which was around day 3, and also the playstyle is really active.

Thought I'd share the idea behind the build I used to get 38 Challenges this league.

Buffs to self-cast this league made me once again reconsider the viability of Fanaticism, a buff intended to be used for self-casters provided by Instruments of Zeal from the Inquisitor ascendancy. Whilst checking up on the wiki page (https://www.poewiki.net/wiki/Instruments_of_Zeal), I noticed under the Version History that GGG opted to specify that Fanaticism grants reduction of all costs (not only mana costs). If you recall, just about every source of generic cost reduction has been altered to only affect life and mana costs because of one abuse case: Chainbreaker, the keystone provided by Akoya Lethal Prides. Fanaticism, along with Saboteur's generic reduced trap cost and the Tireless cluster on the passive skill tree are what I believe to be the only sources left in the game - and Fanaticism provides a whopping 75% reduced cost, which is what I believe to be its strongest aspect.

I decided to build on an older concept seen before - Spellslinger Frostbolt + self-cast Ice Nova. Playing around the cost reduction and the newly released Ashes of the Stars which buffs quality of skill gems, we can once again abuse Divergent Berserk, which gives 18% more spell damage with Enhance before accounting for the helmet buff effect enchant, and also access to the rest of its overpowered quirks such as MORE movement speed, LESS damage taken, and quality of life attack speed for Spellslinger. The results were alright.

POB: https://pastebin.com/4n9huyby

PoE profile: https://www.pathofexile.com/account/view-profile/kaevix/characters?characterName=akoya_fanatic

Pros:

• Very all-rounded character. Good for bossing (nuked 40% more life Kosis in video), good for mapping.

• Self-cast.

• Have to micromanage a fair bit of things (Vortex for Bonechill, Frenzy/Shield Charge for Fanaticism, Berserk, Hatred, Ice Nova for single target, VMS) and you can't spam any of it or your rage goes bye. Most intensive character I've played yet including Warcry Slammers.

• Nobody plays this so I had to craft my gear.

Cons:

• Can't see ground effects.

• Pretty shit without Divergent Berserk/Chainbreaker combo.

• No blink skill (I'm too starved on gem sockets for Flame Dash).

• Self-cast.

• Have to micromanage a fair bit of things (Vortex for Bonechill, Frenzy/Shield Charge for Fanaticism, Berserk, Hatred, Ice Nova for single target, VMS) and you can't spam any of it or your rage goes bye. Most intensive character I've played yet including Warcry Slammers.

• Nobody plays this so I had to craft my gear.

Defensive layers:

• 76% all Ele resists, 75% Chaos resist
• Berserk (26% less damage taken)
• 30% reduced damage from crits
• 54% spell suppression
• 75/75 block with Glancing (with life and ES on block shield)
• 75% reduced effect of curses
• Shock and chill have 0% effect (from pantheon, tree and jewel implicits)
• Freeze immune (from pantheon)
• Elusive
• Petrified Blood
• Decent regen
• Overleech

Offensive layers:

• Divergent Berserk
• RF
• Pain Attunement
• Fanaticism (75% more cast speed)
• Onslaught (from ring)
• Arcane Surge (from Watcher's Eye)
• 15% shock (on block from shield)
• Unnerve
• Culling Strike (from annoint)

Some pointers about the concept:

While the cost reduction is immense, it's still very important to get the rage cost of Ice Nova down to 1. This requires Ice Nova to be maximum 5-linked, so I crafted a Blizzard Crown that gives bonuses to socketed gems from Essence of Hysteria and also spell crit from Shaper influence to make up for it. The benefit is that I end up not needing a 6-link at all (linking Frenzy to GMP increases its rage cost which is very bad).

Do note that Frostbolt which is being Spellslinged does not benefit from the cost reduction as it is not self-casted, so it still costs 4 rage (when linked to GMP). You can opt to drop Spellslinger and self-cast Frostbolt to reduce rage consumption (substitute Spellslinger with Herald of Ice), but then you'd be forced to Shield Charge every second which might force bad positioning (might be L2P issue), and you also lose frenzy charges (can be made up for using a Redeemer Chest) and Mark on Hit applying Assassin's Mark (self-casting it wouldn't be too bad with all the cast speed). As I take Inevitable Judgement, there is no need for Ele Weakness/Frostbite for cold pen (this also nullifies the downside of Blizzard Crown) so AMark is the best curse.

Aside from Chainbreaker, we can also use the cost reduction along with a reduced mana cost of skills flask to get a free aura using the new Divine Blessing support. I opted for Hatred instead of Grace because I'm a softcore player, but more seriously because running both Determination and Grace without Defiance Banner is kinda meh and I generate power charges on block so it's not really that great.

Chainbreaker still does need mana regen investment. The most important ones are on rings (due to Fertile Catalysts boosting it) and on the tree. Due to using Ashes of the Stars, we miss out on a large amount (85%+) of regen that we would normally have. This is best made up for on the tree (75% mana regen from 75% spell block). You will notice that Divergent Berserk does not have stellar uptime - this doesn't really matter because you should consider it similar to a vaal skill. For mapping purposes, it's used just to run faster. For bossing purposes, I turn it on and nuke the boss whilst facetanking due to the insane damage reduction.

Forbidden Flesh and Forbidden Flame are used to get the Fanaticism node as the intermediary Battlemage node is completely useless even if I had T1 flat damage on my wand. Meanwhile, the rest of the points are sunk into Inevitable Judgement and Pious Path which are both too strong to give up for this build.

Single target damage is sort of dependent on Frostbolt projectile speed. Think of Ball Lightning, but worse since I don't link Slower Projectiles to Frostbolt. I use Divergent Frostbolt which with Ashes of the Stars then gives me 50% less projectile speed to make up for this. Clear speed suffers as a result, but Vortex is usually more than enough to clear trash.

Pious Path enables RF and dual life-ES regen. Using the Gravicius chest mod and the hybrid nodes on the tree, I have a decent ES pool despite not having any ES items. Additionally, I have 75/75 block from Glancing Blows and a double life/ES gained on block shield for some more recovery. I end up decently tanky (i.e. facetank release at once Feared), but occasionally I do still die to DoTs if I don't use my life flask to turn RF off in time.

Another spell combo that could be viable (idk) is Spellslinger Phantasmal Unearth + DD or VD. I'm not too sure though.

Thanks to Butsicles for recommending the Divine Blessing tech to run Hatred. Overall, I really liked this build because I like to manage buffs. I chose Wave 30 Simulacrums as a showcase just as I did last league because I consider it to be the hardest content in the game barring deep delving. I'll try my best to answer questions pertaining to the build.