Hollow Zero Master Guide: Unlock Rewards and Dominate ZZZ's Endgame

Hollow Zero is ZZZ's deep endgame system, a sprawling roguelike gauntlet packed with exclusive rewards and brutal challenges. But its complex structure and punishing mechanics can easily overwhelm new investigators. This guide breaks down everything from unlocking the mode to mastering its weekly loops, ensuring you maximize your Polychrome and Z-Merit gains without wasting time.

Hollow Zero Fundamentals: What You Need to Know

How to Access Hollow Zero (Chapter 1 Intermission)

First, you need to finish Chapter 1's main story and a side commission called 'Cat's Lost and Found' - that's your ticket in. Once that's done, you'll hit the Chapter 1 Intermission titled 'Art of War Kite Edition,' which forces a fast-travel tutorial to Scott Outpost.

When you arrive, head straight for the command tent on the left side of the threshold and talk to Ray. He'll permanently activate Hollow Zero for you, and the best part is you can then launch it from any Compendium terminal. No need to trek back to Scott Outpost every single time.

Depths Investigation vs Area Investigation

Hollow Zero splits into two main categories, and mixing them up will send you to the wrong activity.

Depths Investigation is where your main progression lives, housing both Lost Void and Withered Domain - the only modes that increase your License Level. Lost Void is the rogue-like combat gauntlet you'll run for weekly Bounty Commissions, but you can't access it until you finish the 'Mole in the Hole (I)' Agent Story. Withered Domain, on the other hand, uses that Array Mode board of TV tiles and only appears after you hit Inter-Knot Level 20 and finish the Qualification Assessment Commission.

Area Investigation is completely different - it's purely for special events. Think of it as the seasonal content bucket where things like Mystery of Arpeggio Fault appear. You won't grind License XP here; it's just for limited-time challenges and rewards.

As of Version 1.4, the lines have shifted a bit, and Withered Domain now hosts certain special events too, so you'll want to check both categories when new content drops.

Lost Void: The Core Roguelike Experience

Alright, let's break down what you're actually doing inside Lost Void. Once you've cleared the Agent Story 'Mole in the Hole (I)', this whole roguelike sandbox opens up on the laptop in Scott Outpost. It's not just one mode - it's a rotating buffet of pain and rewards, and you need to know which plate to grab each week.

Task Force Investigation (Weekly Boss Rotations)

This is your weekly appointment with suffering, and it starts every Monday at 04:00 server time. The commission sheet is fixed, so you'll always know what's coming, but the final elite node flips between two absolute nightmares depending on the week.

One week you'll face the Miasma Priest, who packs 40% innate Ice resistance but melts if you hit him with Ether or Physical damage. He's got this nasty 'Incantation' move that summons three glyphs; if you don't destroy them within 8 seconds, he gets a massive 50% ATK boost and starts leeching 30% of his damage as health. So yeah, you either burst those glyphs or prepare for a very long day.

The other week, the Wandering Hunter shows up with a different brand of cruelty. If any of your agents are debuffed, he gains 20% damage, which means cleanse supports aren't optional - they're mandatory. Push him to 30% HP and he hits Frenzy, ramping his attack speed by 40% and, here's the kicker, completely disabling all recovery item drops for the rest of the fight.

The loot is worth it though. Weekly clears net you 120 - 240 Polychrome and 6 - 10 Investigation Badges, plus you can snag exclusive W-Engines like 'Hunter's Gaze' and 'Priest's Reliquary' that don't exist anywhere else in the gacha. So you kinda have to show up.

Perpetrator Battle (Agent-Specific Challenges)

Forget your main squad for this one. Perpetrator Battle locks you into a single Trial Agent with a completely remixed kit, curated gear, and mode-specific Tactical Enhancements. You can't just overpower these stages with your own builds - you have to actually learn how these tweaked playstyles work.

You'll need to clear Battlefront Purge once just to unlock this mode, but after that, each stage is a puzzle built around one agent's trial version. During the 'Shattered Edge' event, they added trials for Evelyn, Astra Yao, Jane Doe, and Corin, and these versions sometimes have exclusive moves or passive quirks you won't see in normal play.

Scoring is based on clear time, damage taken, and objective bonuses, so you're rewarded for clean execution. Knock down enough challenges and you'll walk away with Polychrome, Investigator Logs, and Bangbuck for your trouble.

Battlefront Purge (Geppetto Boss Fight)

This is the big one: a 12-floor gauntlet that ends with you staring down Geppetto, the marionette monstrosity. This fight has three invisible HP thresholds that completely change the rules.

At 70% HP, the stage darkens and he starts spawning adds. Hit 40% and he summons an Elite Puppeteer - kill it immediately because despawning the smaller dolls and grabbing a 5-second ATK+50% buff is your window to push the next phase. Drop him to 15% and he enters 'Dramatic Finish,' floating while the arena shrinks; if you don't interrupt him with a Stun codec within 10 seconds, he just executes your entire team.

You're gonna want Fervour III for the ATK boost, Ether Overcurrent III for Ether damage and pierce, or Aegis Field II for shields. First clear gets you 300 Polychrome, 2x Cracked Master Tape, and a Geppetto hologram for your décor collection. Weekly caps include 500 Investigation EXP and 40k Dennies, plus some Tier-III W-Engine fodder.

Shadow Operation (Supply-Based Strategy)

If you're looking for the most efficient grind, this is probably it. Shadow Operation gives you a fixed Shadow Directive Board with three stages that reset weekly. When you clear them, you get Investigation Supplies, and there's a weekly cap of 2,400 that you'll want to hit every time.

These supplies buy everything that matters: Master Tapes, Booster Modules, Polychrome, and W-Engine pods in the Hollow Zero merit shop. But the real secret is that Shadow stages drop purple and gold Resonia more reliably than any normal run, making this the fastest way to fish for specific 5-star Resonia you need for your builds.

They also drop Shadow Crystal Data, another currency you can trade for more supplies or modules. The optimal loop is crushing all three Shadow stages plus one normal run at Intensity 9 - 12, which hits the cap in under 25 minutes. If you're not doing this, you're leaving loot on the table.

Special Operation (Story Content)

This is where Lost Void gets its narrative hooks in you. The whole arc kicks off when an HSO investigator reports that lead researcher Ray has gone missing inside Hollow Zero. After you finish 'Mole in the Hole (I)', check the Hollow Zero laptop in Scott Outpost's main tent - that's your entry point.

Key commissions like Phantom Path and Tracking Down Clues have you investigating data crystals and retrieving a black box, building toward a finale that's essentially a Battlefront Purge boss rush. Clear that and you get a cutscene where Ray is extracted, plus the upper platform of Scott Outpost opens up for better Hollow observation.

One major twist: Lost Void disables the normal Monitor Array, meaning Ether corrosion and squad HP actually carry over room-to-room until you hit a rest site. It adds real stakes to every decision. Finish the story and you'll get a Hollow Anchor furniture piece for your video store, plus a one-time Polychrome payout that's basically a full main-story chapter's worth.

Withered Domain: The 6-Zone Progression System

The Withered Domain is the endgame gauntlet you'll tackle after finishing the main story, and it's built around six distinct zones that ramp up both in difficulty and complexity. Each zone has its own flavor and mechanics, so you'll need to approach them differently.

Zone 1: Qualification Assessment (Tutorial Zone)

The Withered Domain kicks off with Qualification Assessment, which is basically your entry exam split into two halves. The first part, Edge, is a gentle three-floor tutorial that introduces Artifice Resonia chests and throws a Hollow Specimen mini-boss at you - not exactly a nightmare, but enough to make sure you're paying attention. You'll earn 200 Polychrome and 3 Booster Modules for your trouble, which is a decent starter pack.

Then comes Frontline, and this is where the training wheels come off. It adds five more floors, includes a Temporary Partner tile on Floor 1 that can really change your run, and caps everything with the Puppeteer: Threads boss. The rewards jump up to 300 Polychrome and 5 Booster Modules, so it's worth the extra effort.

Zone 2: Old Capital Metro (5-Stage Challenge)

Old Capital Metro cranks things up with five sequential stages, and each one gets progressively nastier. You start with Edge (two floors) and Frontline (two floors), then move into Interior (three floors), Heartland (three floors), and finally Core (three floors).

The difficulty spike isn't just about enemy levels - each stage adds more floors and deeper Corruption-pressure mechanics that'll test your squad's endurance. Luckily, there's a Frontline Supply Outpost rest stop after the Floor 1 Gatekeeper in every stage, so you can catch your breath and adjust your strategy.

The Core stage is where things get serious. You need Inter-Knot Level 50 to even attempt it, and unfortunately, it features two back-to-back boss fights with no outpost between them. This means your team needs to be self-sufficient enough to handle consecutive threats without a safety net.

Zone 3: Construction Ruins (4-Stage Challenge)

Construction Ruins strips away the extra padding and gives you four brutal stages: Frontline, Interior, Heartland, and Core. Each one escalates the challenge in its own way, and you'll need to adapt fast.

Frontline starts you off with two floors to warm up, but Heartland introduces the Miasma Fissure event and a nasty dual boss fight against Executor and Warden simultaneously. Core is the real prize, though - it's four floors deep and ends with the unique Core Devourer three-phase boss, which is as exhausting as it sounds.

The first time you clear Core, you'll get a guaranteed 5★ W-Engine sigil and the 'Architect' nameplate, so it's absolutely worth pushing through the pain.

Zone 4: Abandoned Skyscraper (3-Stage Challenge)

Abandoned Skyscraper condenses the experience into three stages - Interior, Heartland, and Core - that become available one after another, so you can't skip ahead. Interior acts as a scouting stage with basic Resonia drops, letting you test the waters without too much risk.

Heartland adds Hollow Corruption tiles and supply outposts, which means you'll need to manage your corruption levels while grabbing resources. The Core stage doesn't mess around: Floor 1 hits you with elite packs right away, and the final boss has a two-phase fight with a 35% phase-shift that can catch you off guard if you're not prepared.

Zone 5: Withering Garden (Resonia Preparation)

Withering Garden is completely different - it's a single-stage zone designed purely for Resonia kit preparation. You run through three rooms, and if you clear Withering Garden - Core once, you gain access to the 'Save Kit' button.

This is huge because it lets you store powerful Resonia combinations for Inferno Reap. You can select Intensity levels 1 - 11, and if you crank it to 9 - 11, you're guaranteed gold Resonia drops. This zone is basically your workshop for building the perfect loadout for the final challenge.

Zone 6: Inferno Reap (Nineveh Boss Fight)

Finally, there's Inferno Reap, the sixth and final zone. This is a 90-second DPS check against an undefeatable version of Nineveh, and your rewards are based purely on total damage dealt.

To even access it, you need Inter-Knot Level 42 and must have completed a Withering Garden - Core run. The damage tiers are brutal: hit 30M+ and you'll earn 200 Polychrome, 5 Master-Copy, and 40k Dennies, but even 5M+ gets you 50 Polychrome and 1 Master-Copy.

Here's the catch: Nineveh's HP multiplier increases by +2 each retry, capping at 12× maximum. This means saved Resonia kits from Withering Garden aren't just helpful - they're absolutely essential for leaderboard runs.

Optimal Resonia Drafting Order (Patch 1.4 Meta)

First things first - you're not just grabbing whatever glows gold. The meta's shifted hard in 1.4, and your drafting order can make or break a run.

Attribute DMG +25% (Gold) is your absolute first pick, no contest. These scale multiplicatively and actually give you about 18% more effective damage than ATK% cards once you factor in the new RES curve. If you're running Ellen, that Ice DMG card isn't just nice - it's mandatory.

After that, you'll want HP (Purple). We're talking a jump from 5k to 6.7k effective health, which is the difference between getting one-shot by a three-hit combo and surviving with enough time to pop your Sustain Plug-in. Flat HP or % HP both work; just grab whichever shows up first at A-rank or higher.

Third priority is Shield on Kill (Purple). This one's more of a luxury - it spawns a 400-600 HP shield after every kill and stacks up to three times. The catch? It decays after five seconds, so it's really a 'win-more' buff that keeps your momentum going. Nice to have, but not core.

Here's what you should skip: Agent-specific buffs. They're still bugged in 1.4 and just don't work reliably. Don't waste a draft on them.

One last thing - only S-rank Gatekeeper kills count toward your weekly 900 Z-Merit pool, which means you don't need to full-clear every tile. Just get in, get your kills, and get out.

Zone-Specific Team Recommendations (F2P & Premium)

Hollow Zero isn't just about picking your favorites - each zone has specific weaknesses you can exploit. Here's what actually works.

Ice Veil Zone is where premium players shine with Zhao (Def-Ice) • Ellen (Attack-Ice) • Lycaon (Stun-Ice). That synergy is brutal. If you don't have Lycaon, swap in Soukaku (Support-Ice) for the F2P mirror - she still gives Ellen the buffs she needs. Keep Anby (Stun-Electric) as your third if you're really scraping by; her stun is too good to give up.

For Electric Storm Zone, the premium comp is Grace (Anomaly-Electric) • Anton (Attack-Electric) • Anby (Stun-Electric). Grace's anomaly procs carry hard here. The F2P version is nearly as good - just replace Anton with Rina (Support-Electric) and keep the other two. You lose some burst, but the core rotation still works.

Fire Blitz Zone rewards pure fire damage. Premium runs Miyabi (Attack-Fire) • Manato (Attack-Fire) • Koleda (Stun-Fire), but the F2P mirror is surprisingly solid: Manato • Soldier 11 (Attack-Fire) • Ben (Def-Fire). Ben's defense buffs make up for the lack of Miyabi's raw damage, and Soldier 11 still slaps.

In Physical Rending Zone, you want Jane (Anomaly-Physical) • Nekomata (Attack-Physical) • Nicole (Support-Ether) for premium. For F2P, Piper (Anomaly-Physical) • Billy (Attack-Physical) • Nicole gets you 80% of the way there. Piper's anomaly application is slower, but Billy's consistent damage keeps you stable.

Finally, Ether Void Zone is tricky. Premium runs Yixuan (Attack-Ether) • Lighter (Anomaly-Ether) • Qingyi (Stun-Ether), but most F2P players will use Lighter • Qingyi • Nicole instead. You lose Yixuan's burst, but Nicole's ether support keeps the team functional until you pull a better DPS.

Pathing Efficiency: The 6-Minute Z-Merit Loop

Look, you don't need to spend hours in Hollow Zero to hit your weekly cap. The whole 1900 Z-Merit grind can be done in about ten minutes if you're smart about it.

Here's the loop that actually works:

Start Inferno Reap - Geppetto VI. As soon as you load in, take the leftmost portal to Old Metro - this skip still gives the fastest elite-density layout, and the merit coefficient hasn't changed since 1.2. Grab Rapid Echo 1 if you see it, but don't waste time shopping otherwise.

Your only goal is three S-rank Gatekeeper kills (that's your 900 weekly cap from clears). First, head straight to Gatekeeper β for 300 merits. After that, hit the shop, reroll if you've got the cash, then find the second Gatekeeper β for another 300. Reroll one more time and hunt down Gatekeeper α for the final 300.

Once that third boss drops, select 'Claim & Retreat' immediately. Don't loot extra tiles - it's wasted time. Log those 900 merits, then head to your weekly bounty commissions for the extra 1000. Done. Ten minutes, 1900 Z-Merits, and you're free to do something else.

This method only works because the cap is 900 from Gatekeepers and 1000 from bounties. Full-clearing rooms is for people who don't value their time.

Investigation License: Level Progression & Rewards

Every level in the Investigation License costs exactly 1,500 points, but here is the good news: you cannot lose progress, so there is no de-ranking if you have a rough week. Each time you hit a new level, you will grab some Polychromes, Boopons, and Z-Merits as baseline currency.

The real juice is in the exclusive cosmetics. You can earn Brawlerboo (a unique Bangboo skin), animated emotes like Booressure, plus custom namecards and avatars. On top of that, the track throws in convenience items such as Victoria Housekeeping Coupons and W-Engine modules.

Weekly Caps: 5,000 Investigation Points & 8,000 Z-Merits

You can only earn 5,000 Investigation Points per week, and any extra you might squeeze out simply vanishes - it does not roll over, so do not waste your time grinding past the limit. Z-Merits have their own separate cap of 8,000 per week, which comes from Gatekeeper S-rank clears (1,900) and Bounty Commissions (6,100).

Both counters reset every Monday at 04:00 UTC, which means you need to plan your farm sessions around that clock. Once you see the warning that you have hit either cap, stop and save your Batteries for next week.

Bounty Commissions & Casper's Shop

Bounty Commissions are your main weekly tasks for Z-Merits, and you can knock out up to three Common commissions (which you can refresh) plus four Special commissions each week. Once you have stacked those merits, head over to Casper's Shop at Scott Outpost to spend them.

Casper trades Z-Merits for Master Tapes, Boopons, and straight Dennies at a fixed rate of 20 merits for 6,000 Dennies. The shop also stocks upgrade materials and W-Engines. If you are low on cash, there is a fast Denny farm: load into Construction Ruins: Interior, collect 150 Z-Merits, then retreat to refund the Battery you spent.

Collection Rewards: Resonia, Corruption & Lost Items

Besides the level track, Ray at Scott Outpost runs a Research Log that tracks your collectible progress. He keeps tabs on every unique Resonia, Corruption effect, Lost Item, and Special Area you discover, and each new entry unlocks a one-time reward parcel.

First-time Corruptions (like Miasma I) grant Polychromes and upgrade mats, while clearing Special Areas such as the Old Capital Metro hidden vault gives first-clear bonuses including W-Engines. Completing Resonia sets - for example, grabbing every Onslaught S-rank - yields Polychromes and permanent run buffs. Some of these, like Bounty Corruptions and Lost Items, are also weekly replayables that give recurring Polychromes and items.

Common Pitfalls & Pro Tips

Top 5 Mistakes to Avoid

1. Hoarding coins for that 'perfect' final shop will kill you faster than any boss. Hollow Zero's Corruption scales exponentially - your 12 Corruption becomes 24 on the next sector transition, then 48, then you're just dead. Plus, for every 100 unspent Resonia after Sector 2, corruption ramps 15% faster, so you're accelerating your own demise. Spend everything down to under 200 before exiting any sector.

2. Taking 'low-HP = damage' Resonia without shields sounds like a glass cannon dream, but it's a nightmare without reliable shield generation because one bad hit ends your entire run.

3. Not quitting immediately after a boss death burns roughly 25 seconds each time. There's no reason to watch the death animation when you could be resetting and trying again.

4. Ignoring weekly caps costs you 1,200 Polychrome every week since the bounty snapshots at Monday 04:00 UTC and deletes any unfinished run along with your tier rewards.

5. Using agent-specific buffs is just wasting a slot right now - they're bugged and don't function, so you're basically running with one fewer Resonia.

Advanced Optimization Strategies

• Start with a 'battery' Agent like Rina, Soukaku, or Soldier 11. This lets your rogue deck focus purely on scaling damage instead of patching resource holes, which means you can stack offensive Resonia much more aggressively.

• Bangboo > Agent synergy in Hollow Zero. Prioritize Avocaboo for the heal-on-kill if you need sustainability, or Rocketboo for the 20% ATK boost after a chain attack if you're speed-clearing. Your Bangboo choice matters more than your team composition.

• The 45-second enrage timer is everything. Elites and the Zone 6 boss enrage after 45 seconds, so you need to design your team around a single, uninterrupted 40-second burst using Battery → Stun/Anomaly → Main DPS rotation. If you can't kill them in that window, you need more damage.

• Restart if the first shop doesn't offer your counter Resonia. Curse colors cycle every two floors, and the DPS check at 4-3 assumes you have it. If the shop doesn't match, you're already behind the curve and might as well reset.

• Only upgrade Gold Resonia - Silver and Bronze are a waste of resources long-term, so save your cash.

• At Inter-Knot 40, use Auto-Sim for AFK farming. It won't play perfectly, but it'll grind while you're doing something else, which is pure efficiency.

• Short, high-risk stages beat long, safe runs for Z-Merit efficiency. The merit-per-minute is much higher when you're pushing danger zones.

When to Farm vs When to Push Progression

Your optimal weekly schedule is all about Monday efficiency. The weekly bounty pays 1,200 Polychrome and snapshots every Monday at 04:00 UTC - any unfinished run gets deleted, so you want to cap early.

Day	Focus	Why
Monday morning	Clear highest NEW zone once on Normal	One-time chests give 200-400 Poly + big Z-Merit bundle
Monday afternoon	Farm Zone 4 Hard until weekly cap	Bounty expires in 24h; get your 1,200 Polychrome
Tuesday-Sunday	License progression or specific bounties	Time to experiment or push higher zones
Post-License 40	Zone 4 Hard forever farm	Zone 5 takes twice as long for <10% more merit

Here's the thing: most players treat Zone 4 Hard as the forever farm once they've grabbed their one-time chests. The merit difference between Zone 4 and 5 is under 10%, but Zone 5 takes almost twice as long to clear. License 40 unlocks the final Zone 5 and a cosmetic badge - clear it once for the bragging rights, then fall back to Zone 4 for efficient farming.

Mastering Hollow Zero is about understanding its systems, not just brute force. By focusing on efficient pathing, smart Resonia drafting, and respecting the weekly caps, you can secure all the exclusive W-Engines, Polychrome, and cosmetics with minimal grind. Now, head to Scott Outpost, activate your License, and start your climb.