Impossible Challenge

I recently completed the impossible challenge and thought I'd share some of my findings and strategies.

The impossible challenge includes enemies with more actions, bonus actions and a lot more HP. There's a few other good posts around this on the subreddit, and Morgana evelyn has streamed her run.

My main goal was to be challenged and be able to min max a little more than usual, retaining the party building aspect, without trivialising the content.

This was one of the most fun runs I've done, and easily my longest (well over 200 hours, most of which was spent in act 1).

Restrictions

I avoided anything that, entirely subjectively, felt too much like cheating to me. So I allowed scrolls, arcane acuity, all gear (including rushing them as soon as they are available), consumables, but didn't use darkness, camp casting (with one or two exceptions), barrelmancy, or outright exploits (well, many). I had warding bond up throughout but brought a long a cleric running it. I also trialled Remus' arcane ward abusing druid build - very powerful but exploiting to get the stacks wasn't satisfying for me within the scope of this challenge, so I canned it after a fight or two. Did look fun for a slayer form durge run though.

In hindsight, I'd probably ban globe of invulnerability next time too.

I used several QoL addons:

• Automatic / permanent longstrider/enhanced leap / featherfall
• Weightless + infinite gold. Gold is functionally infinite anyway with the hexblade exploit and/or pickpocketing.
• Extra adamantine ore. I got this in case I wanted to trial the adamantine shields, which is my usual choice. I ended up not even crafting more than the usual 2 as adamantine heavy armor was so effective.
• Infinite camp supplies. Already pretty trivial to get as many as you like. Also pointless for me since I avoid long resting as much as possible, but hey, I had it.

Act 1

This is easily the hardest part of the challenge. In act 2 but especially act 1 I rotated builds a lot on a per fight basis. In pretty much every party setup I included a titanstring archer (arcane archer early on, gloomstalker from 8-10, EK 11 onwards) and something with at least 4 levels of cleric for heavy armour proficiency, warding bond, and heavy armour mastery (feat).

Act 1 builds

Act 1 I mostly used:

• Titanstring arcane archer. Using bane on hit and rider gear.
• Life Cleric4/div wizard multi. Warding bond on whole team + adamantine armour + HAM on whole team. Responsible in act 1 for keeping people alive with the usual on heal buff gear, and scroll or hard casting sleet storm largely.
• Berserker barb - necessary damage.
• Monk - only from level 5. Stunning strike was very potent in this setup.
• Duergar shove thief. Used to safely farm XP from level 4-5 and clear out Duergar in Grymforge.

I experimented with a few others:

• Warlock for hunger of hadar. Was strong but ran into damage problems. 10 turns of hadar + sleetstorm isn't actually all that much when you have two (cleric, warlock) low damage characters.
• Bard archer - I found this pretty underwhelming. Low damage (titanstring was taken) and squishy.
• Druid - I think this one does have potential. I thought TB + spike growth would be a solve for early act 1, but the combination of low AC + concentrating meant this was squishy, even with the extra health. Would try this again and build around it a little more next time, there is potential.
• Abjuration - I thought this would be really strong with retaliation damage scaling with enemy actions. But early on this just crashed and burned. Not enough stacks to last back until your own turn again. Not enough damage when AoA goes down quickly either. Also fairly tedious to play. This one probably also has potential if you're building around it.

Main solves

• Warding bond + Heavy armour master on the cleric and fighter + adamantine plate. This made the fighter functionally immune to most enemies.
• Gravity. By far the most damage done in this act. I had elixir of strength on all characters, and the most impactful action most of the time was throwing. Even for the archer in certain key fights like the grove defence, throwing a goblin far enough is just higher impact than a shot from titanstring in many instances. Was also a good use of action + bonus action (shove) for the cleric a lot of the time.
• Out of combat cheese. I used minor illusion + shove thief to pick off stragglers where I could.
• Scroll of sleet storm. Fairly self explanatory.

Act 1 : Route / main fights - pre goblin leaders

• Started as sorceror with enhanced leap / feather fall.
• Avoided/ran past final combat in the nautiloid.
• Skipped grove door fight by stealthing / jumping around the outside.
• Did a non-combat route to hit level 4 and get two copies of adamantine plate, cheesing the Grym fight. (Although, this got hairy when the fire mephits spawned. I threw them back down to Grym who took care of it).
• Githyanki patrol: skipped this to get XP
• I didn't quite get to level 5 since I hadn't reviewed the optimal route beforehand or done that before. Once I had the fighter / cleric combo ready and double adamantine plate I started to take easier fights like goblins.
• Seeing the efficacy of the damage mitigation, I decided to take on the owlbear at level 4 and was immediately humbled. The bard archer and throwzerker were pretty much immediately gibbed. It was a very long fight (no extra attack) with the archer fighter whittling them down while trying to kite and healing with potions. Cleric ran away almost immediately to give me an insurance policy.
• I did some thief / minor illusion shove cheese to get to 5 safely after that.
• Tried hadar/sleet storm combo and ran into damage issues. Pivoted to throw barb / monk / cleric / fighter archer which handled most of the rest of the act.
• Goblin leaders: Minthara was handled at the grove defence. I let priestess glut capture me to automatically handle her. For Dror I opened with surprise and MVP banishing arrow on him allowed me to use gravity (and the spiders) to take down everyone else first.
• Grove defence. This was a complete bloodbath. I hadn't really done the grove defence before, so thought impossible challenge honour mode was the natural time to start. I hadn't appreciated that despite killing everyone I could find in the goblin camp, there is a large amount of enemies and they are thrown onto the battlements. This was like defending helms deep and was one of the closest fights of the whole challenge. I used the ogres here but even so most of the grove were killed in the valiant defence. Most rounds consisted of trying to cc the spiders up on the battlements, throw the goblins that had made it up back down onto other goblins for damage and prone, and desperately try to heal up the vast amounts of incoming damage. It felt like forever but eventually we won, though with all the corpses of grove inhabitants around us it was a somewhat pyrrhic victory.

Act 1.5/2

• With timebound content out the way I immediately progressed to act 1.5 and act 2 to get lots of new gear. Big ones being everything from act2 vendors and the hat of arcane acuity.
• At this point I switched to bow of the banshee bard archer with hat of arcane acuity, drakethroat ice + snowburst ring for control. Arcane acuity in act 1 is pretty gamebreaking and a little exploit-y, I admit. Ice pools from the bow shots, fear and sleet storm everywhere largely handled all remaining act 1 fights like the gnolls - except Ethel.
• Of all fights the eagles at the top of the creche was harder than expected. You lack the damage to kill them before they can summon friends, and crucially they are immune to fall damage. This fight was a drawn out slog relying on heavy armour mastery mitigation and the fighter brute forcing it.
• I unintentionally cheesed the inquisitor. I made a mistake in getting a surprise round and decided to reset, but with all of the bonus actions the inquisitor and friends managed to travel from the room all the way out into the bridge in a single turn. So I improvised and used the power of chasms, paying the price of losing out on the diadem of arcane synergy.

Act 2 builds

At this point I started to add a few more builds into the mix:

• Heavy armour radiant orb monk. Credit to Morgana for this one, it's very effective.
• Ultra high AC and saves paladin with the radiant reflection helm from the creche. This character was immune to attack rolls and was a pretty effective and safe solve for lots of fights. I also used this character to take on Ethel solo. The hag clones all instantly killed themselves with the radiant reflection, and Ethel's only option was to fire off the relatively weak vicious mockery cantrip. With warding bond, and high paladin saves, this did minimal damage.
• Fire sorceror. This got more useful as I started to get more spell slots around the level 8-9 mark. I didn't multiclass with warlock, preferring scrolls of confusion (S+++ tier spell in this mode given it scales with enemy damage) and the higher casting level.
• Switched the fighter to a gloomstalker assassin archer. It was a little underwhelming in this mode to be honest. While forced crits are never bad, the HP pools you're dealing with make it less effective.
• Duergar hireling shove thief with the bull cloth. Used to clear out no name NPCs in moonrise as much as possible as before, largely to save time.

One of the things I really like about this challenge is it forces you to not take any encounter for granted. Two no-name guards in moonrise managed to instagib the monk by war cleric +attack roll comboing into a crit thundering smite + shove pushing into a chasm. Equally I got too cocky with the paladin taking on the karniss convoy and got mass shoved into a chasm.

Main solves

• Ultra high AC
• Radorb stacking from a monk or paladin
• Arcane acuity
• Confusion. Works versus undead. AoE, doesn't hit allies, scales with the enemies damage. Hugely powerful spell in this format.
• Scroll of globe of invulnerability (one or two later fights)

Rest of act 2

• I talked down the various thorms, mostly to save time.
• Githyank ambush was solved by the fire sorceror. Minor illusion + fire acuity + confusion, I don't think they got to a roll single attack roll. This was a glimpse of things to come in act 3.
• Shambling mound. For this one I surprised everyone else and triggered a mass explosion from the plants to take down the vast majority of them, bard ice proning the remainders. The mound itself is vulnerable to hold monster, so the fire sorc was on CC duty just for him. Even forcing crits from hold monster and firing full spell slot scorching rays crits into the mound, it took several rounds to bring down.
• I cheesed the Halsin portal defence. I realised that if I waited for long enough in the act for level 6 spells to start to appear, I could cast an extended globe of invulnerability around the portal itself and defend it trivially. Some of the wraiths had attacks that went past the globe, one of the stat drains, but that was easily dealt with. Next time without using globe I think I'd try to block in with walls of x spells a little more and sleet storm + hadar. As soon as the fight was over I needed to use another globe to prevent Halsin suiciding on the remnants of a wall of fire (learnt this the hard way the last honour mode run...) but all fine.
• Cleared out all of moonrise as safely as possible with the shove build, then picked off the remainders with the main party. I also cleared all of the roof top with the thief shover, after isolating Ketheric.
• Did the last light defence. I kidnapped everyone I cared about here (vendors) and brought them to the gauntlet of shar, and used invisibility + sanctuary to prevent isobel from dying.
• Around now I entered the gauntlet of shar. The sharran prior to Balthazzar took a long time, since I couldn't kill the globes fast enough to stop them spawning all of the adds. Not that I particularly wanted to either, as I was trying to maximise XP if possible. This fight took forever though. Lots of wall of fire kiting back down past the trial rooms.
• Stripped party naked for the reflection trial and surprised them. Pretty straight forward.
• Decided to leave Balthazzar until the Shadowfell to maximise XP. In hindsight this was a mistake as this was a very hard fight and one where I genuinely feared for the run. Was the first time I really needed to use globe heavily. I don't think I'd ever fought Balthazzar here before in previous runs, and hadn't appreciated that there is a lot of adds. Globe being ever powerful got us through as we picked off the adds slowly until killing Balthazzar himself.
• Yurgir fight was straight forward. Controlled yurgir while novaing the rest of the enemies with gloomstalker and wet + chain lightning (scrolls) nuking.
• I messed up the morninglord radiance buff by coming back to act 1.5 to take on the death shepherds, resulting in another forced rest I hadn't accounted for. Bummer.

Myrkul

Then it was a question of preparing for the illithid colony and Myrkul. Myrkul was a fun fight to prepare for, I spent a fair amount of time strategising it and had a fairly extensive checklist to get ready. Experience honour mode players will know the main things that solve this fight, but to summarise the main ones:

• Mindflayer has to die as soon as possible. I decided to make this easy and just throw it off into a chasm, but I was ready with speed potions and gloomstalker burst to bring it down.
• Greater and lesser elementals from scrolls are very useful to take down the necromite eggs and bait out the legendary reaction.
• Damage: Arrow of undead slaying + Ne'er misser. Wet + high level lightning spells.
• Control: stunning strike. Radiant orbs. Arrow of darkness onto Myrkul. Command: drop on the scythe, boosted with fire acuity. At some point prior to Myrkul I decided that the fire sorceror was too squishy and the wizard/druid (stars) levels on the cleric weren't leaving with me very impactful actions. So I combined them. 4 cleric/6 fire sorcm playing largely like a fire sorceror but sitting in heavy armour with warding bonds on the party and heavy armour mastery.
• Doomhammer. Wielded by an EK (switched out the bard archer for this fight) for all of the attacks. Contingency in case I couldn't deal with the necromites, but wasn't necessary.

I probably overprepared for this one in all honesty, it didn't really feel very close. It was nowhere near as difficult as Balthazzar, for example.

I'll be honest, that's pretty much functionally the end of the run. As soon as I entered act 3 I beelined towards all the overpowered gear options and entered god mode. But I'll summarise anyway...

Act 3

• Re-specced to make sure I succeeded the persuasion checks to take half illithid form on all companions. The cleric had the awakened buff from the creche too - forgot to mention that.
• Farmed all the Rivington vendors and used Duergar invisibility + flight to skip straight to the lower city. Farmed all vendors there too, grabbed Marko, amulet of the devout, became an unholy assassin and grabbed all of the overpowered bhaalist gear. Came back to Rivington and grabbed helm of balduran, skipping ansur for now. I deliberately failed the challenges and ran through invis to save time. Grabbed band of the mystic scoundrel and nyrulna and respecced everyone, hitting level 11 at some point into the murder tribunal I think.

Act 3 builds

I barely needed to make any changes to these four. We just walked into most fights, often without resting while down on spell slots, and ran over them:

• Control: 12 bard archer. I wasn't resting very often, and in this challenge the value of the nova round is diminished. I tried a few different options but ultimately landed back with bow of the banshee + acuity + drakethroat ice + snowburst, and stacked DC gear. Feats were alert, ASI CHA for spell save DC and dual wielder, running rhapsody and one of the spell save DC staffs. BotMS user.
• Control: 4 cleric 8 fire sorceror. Played like a traditional fire sorc, for the most part. Swapped in some damage pieces where needed. Also respecced out of life cleric because we were taking very little damage at all as a party, went with tempest for twinned marko chain lightning nova options. Spell save DC, heavy armour, but that aside largely core fire sorceror items.
• Damage: EK archer. Was it really going to be anything else? This should have been 11 EK / 1 war cleric, but I realised that too late so it was a straight EK throughout. Bhaalist armour, as many riders as possible. This fellow deleted full impossible challenge buffed up Raphael in one round. It's notorious for a reason.
• Damage: EK 11/1 hexblade shadowblade. Maximum AC gear and brain drain gloves (you weren't planning on passing any of the controllers saves, were you?).

Everyone had alert.

Act 3 Gameplay loop

Most fights went something like this:

• Bard and fire sorc cast hold monster or hold person on a few key targets, else confusion.
• EK archer use slaying arrows or AoMT into the held target to delete the biggest threat
• EK shadowblade focuses on big threats that can't be as easily controlled/brought down fast. As well as doing silly damage, he's also unhittable and can block enemies from getting through. Used this for the Viconica fight for example.

After assembling the dream team we started killing all of the bosses, not even bothering to reach level 12 - it wasn't necessary.

Orin fight was trivial since I was Durge and speared the nightsong (forgot to mention that). Used the EK shadowblade build with acuity and BotMS equipped, forcing an initial crit with the illithid power and surgeons amulet combo. The damage was so high that a follow up cast wasn't even needed, action surge and two rounds worth of shadowblade crits were enough.

Other fights

• Cazador: I unintentionally cheesed this one. I wanted to start the fight by getting rid of the eyebite caster, but in doing so grouped them up and thunder wave was able to actually clear out the vast majority of the fight less Cazador. The fight itself became the loop I describe above with Otto's irresistable dance as the control spell of choice.
• Ansur: regular loop + confusion. Used globe for good measure.
• Raphael: I heavily over prepared for this one. Took inspiration from Morgana and brought a full retinue of elementals with the illithid shield up (the long rest faucet). I also skipped all of the NPCs here with invisibility, because by this point I was getting close to the end. Convinced Yurgir to join my cause, hold monster on Raphael, full nova from the EK archer single handedly deleted Raphael in one turn with slaying arrows. He did something like 2300 damage, that kind of ballpark. Rest of the fight was trivial and easily controlled. I let hope sit in a globe of invulnerability since otherwise she'd probably just get gibbed.
• Sarevok: killed in one round, same as above.
• Gortash: this one was actually interesting, because a) I messed up and slipped on my own ice fields and b) the NPCs here have control spells. This was one of the fights where we came closest to wiping, all it would have taken is a few more failed saves against the command: grovels coming out. Despite having alert, Gortash outsped most of the team but not the archer, so the combo wasn't quite as fluent as in other fights. We had a clutch globe of invulnerability from the EK archer to protect the others at one point.

At this point I decided the run was functionally over and just headed straight to the brain, skipping everything else. I prepared for the brain fight but Gale ultimately allowed me to skip. I find this one of the more tedious fights so I generally skip it on my runs if I can.

Reflecting on the challenge

There were effectively four different power break points:

• Level 5: access to elixir boosted stunning strike, sleet storm + hunger of hadar.
• Post goblin leaders: access to act 2 gear and arcane acuity/snowburst/banshee combo for mass skipping enemy turns. You also start to find arrow of many targets around this point, to make it even stronger.
• Level 8-9: at this point you start to get enough spell slots that one of the other ultra powerful builds comes online - fire sorceror. I didn't bother with warlock multi, preferring to use confusion and sacrifice my concentration slot.
• Rivington: at this point the challenge effectively ends and your party reaches god status.

Power levels of the various overpowered mechanics

Based purely on my subjective opinion in this challenge, I'd rank the overpowered mechanics like this:

1. Scrolls. These are 'just' very strong in act 1. Largely sleet storm and misty step. But in act 2 and especially 3 it's completely game breaking. Everyone, caster or otherwise, has unlimited disintegration, chain lightning, globe of invulnerability (!), confusion spells ready to go. Casters are a little less powerful in this mode in a sense, because the HP pools means spell slots being a limited resource is actually relevant. But scrolls completely negates that. They are also magnified by the second item on this list.
2. Arcane acuity. This isn't in the first spot because it isn't available for the hardest part of the game, and is also competing against globe of invulnerability in act 3. However, it is a big proponent for completely solving the big fights in act 3.
3. Consumable arrows. Next time I would be tempted to swap out the EK shadowblade user for another archer, because piercing + crit + slaying (or AoMT) arrows are just silly.
4. All other consumables. Potion spam was pretty necessary in act 1, and likewise strength elixirs.
5. Tavern brawler. I didn't use it that heavily in this run, honestly. It did some reasonable damage in act 1, but it wasn't as powerful as the warding bond backed archer - in my opinion. The best user IMO is a monk, but by the lategame monk is a somewhat reasonable controller with cloud giant backed stunning strike also doing fairly good damage, but both control and damage pales in comparison to more specialised options. BoMTS and/or fire acuity abusing control is more reliable and battlefield wide, and slaying arrows into piercing vulnerability is just a completely different level of damage.

The 'strongest' party discussions

My act 3 party is ultimately just a bunch of meta builds slapped together. But after running this challenge I now strongly believe to be even considered for the title of strongest party, a party needs to be strong in act 1, because it's pretty difficult not to steam roll act 3, certainly in regular unmodded gameplay. I haven't run it myself but I suspect that means a darkness party is objectively the best looking holistically across the whole game.

What next?

Well for me I've started to relax into a regular honour mode run with RP builds. It's a nice change of pace after the hectic act 1 bloodbath of the impossible challenge. I may also look at optimising act 1 impossible challenge, inspired as I said by grousedrum.

This post was a lot longer than I intended! Ended up being a brain dump, hopefully it's useful for anyone else taking the challenge in future. It was a LOT of fun and I'd strongly recommend it!