Hollow Deep Dive System Complete Guide

Hollow Deep Dive System is the main game mode in Zenless Zone Zero. In simpler terms, this is where you'll be completing the main mission and side mission to obtain rewards.

Hollow Deep Dive System is the main game mode in Zenless Zone Zero. In simpler terms, this is where you'll be completing the main mission and side mission to obtain rewards.

Story - Main Commission

The main commission is where you follow the main storyline of Zenless Zone Zero. To keep this spoiler-free, I won't touch the storyline. The difference between this game mode and others is that you can use the trial characters (story-limited agents like Nekomata). Of course, you can turn off that setting to use your own characters as it won't affect the storyline.

Most importantly, many stores and other game modes are locked behind the Main Commission, so it's better to complete this one first so you can enjoy the rest of the game.

Last but not least, you will get many free characters from the Main Commission, namely Anby, Billy, Nicole, and Ben. They're only A-Rank Agents, but hey, beggars can't be choosers right?

You can browse back to all the stories by going to the Commission Log on the shelf beside the television. Aside from watching the cutscene again, you can also gain rewards after completing them; which are the delicious Films and Dennies.

The icon to claim those reward are by clicking on the ZZZZ icon at the bottom left, which is pretty small and might not be noticeable at first glance.

Gameplay in the Hollow Deep Dive

When you enter any stage of the Main Commission or Side Commission, you will notice that you'll be moving through the many MANY televisions (officially called the Board) and you will be controlling Bangboo Eous to move through the terrain. There are many types of terrains in the HDD - from healing your characters, collecting observation data, and most importantly; fighting enemies and bosses (the red television like in the image above). You can check all of them in our Fairy Library: Hollow Exploration Guide.

In certain stages, there will be mechanisms where you need to pay attention to Pressure and Corruption. By moving through the Hollow terrain - every step you take, you will increase your Pressure bar (10 Pressure per step).
When your Pressure reaches 100, your squad will experience Pressure overload and gain a random Corruption, and their pressure will be reset to 0.

Corruption is akin to debuff (or buff if we're looking positively) and this game has a variety of it. For example, you can get a Corruption: Sharpened Pain, where both enemies and allies gain a Crit DMG Bonus. Look in the image above, both we and the enemies got Crit DMG Bonus, that's fair in my opinion so I would think it's a buff.

  • Corruptions can have adverse effects on both combat and exploration. You can check the details in the Corruption tab.
  • Once your squad accumulates five Corruptions, further Pressure accumulation during exploration will result in a proportional loss of HP.
  • If your squad members' HP drops too low, the exploration will be terminated prematurely.

I mentioned that you can get this mechanism in certain stages. Now how do you know which stage has this mechanism? Easy, just look at the pressure bar of the stages in the HDD.

The pressure bar of the HDD indicates the current pressure level experienced by Agents within the Hollow. Ether activity varies across different Hollows, and Agents operation in Hollows with a higher level of Ether activity will encounter more intense pressure.

Hollow activity level is low and won't cause Pressure.

Hollow activity level is moderate. Certain areas may cause Pressure.

Hollow activity level is high. All areas will cause Stress.

Side Commission

Side Commission is as the name suggested, side commissions. You can start a side commission by going around the open world and talking to NPCs with obvious marks above their head.

Once you talk to them, you can check the commission from the Side Commission and complete them to get the corresponding rewards. Among the commissions, some will unlock various stores in the open world (like 141 Convenience Store, Waterfall Soup - Noodle Soup, etc.) so keep that in mind and you should start collecting Side Commissions.

Rally Commission

The last mode is the Rally Commission. In a way, it's like the usual battle mode with a hint of combat tutorial - ONLY battle mode, where there won't be navigation through the television like the Main and Side Commission, and you'll just defeat enemies left and right.

As your Inter-Knot Level increases, new difficulties will become available for Rally Commissions: Basic, Intermediate, Advanced, and Expert. Reminder: The more difficult the commission, the better the rewards, and the more Battery Charge required.

Types of Rally Commission

There are four types of Rally Commissions that you can take on:

  1. Perfect Assist: Metro Zone
  2. Vital View: Scrapyard Zone
  3. Depth Exploration: Construction Zone
  4. Triathlon Rally

Some of the Rally Commission has special Commission Features, which it will grant certain effects to all allies during the commission - which may be a buff, nuisance, or both. You can check the features in the Details Screen before the commission begins.

Rewards for Rally Commission

By completing Rally Commissions, you can obtain Plating Agents which are needed to Tune Drive Discs, as well as Inter-Knot Credits. Completing a Rally Commission for the first time will yield bonus Film and other upgrade materials as rewards.

Complete Advanced and Expert Rally Commissions to get upgrade materials needed for advanced Agent Skills - Rally Records.

There are also Mini Cargo Trucks hidden along the way during Rally Commissions. Earn bonus rewards by opening them.

Hollow Zero

I unlocked this mode after completing the first Rally Commission 'Perfect Assist: Metro Zone - Beginner' where Shepherd comes to our store and relays the big news. After that, this mode is unlocked.
Update: From the official announcement, you will receive the first exploration commission for Hollow Zero after completing the commission "Earlybird Ticket to Safety."

Team Setup for Hollow Zero

For this game mode, dare I say, is like the equivalent of Genshin Impact's Spiral Abyss. The unique gameplay of this mode is that only one agent can enter the Hollow as the "leader" at the start of a mission, and other agents can enter to support once more areas have been explored and stabilized.

  • Before entering Hollow Zero, designate 1 Agent to be the Leader, who starts exploring alone.
  • When exploring the Edge, you can designate 2 Agents as Backup. If you didn't add any, you can't call for their help later.
  • As explorations go deeper, more Backup slots open up, and more Agents can be set as Backup.

When entering Stable Areas in Hollows, you can make a Random Call to 1 Backup Agent to come in as reinforcements.

If you don't currently need an Agent's support, you can record the Agent's message to your Reinforcement Beacon Bangboo Plug-In. If you do need an Agent's help later on, you can use a Reinforcement Beacon to instantly call a Backup Agent to come in to help you.

Exploration in Hollow Zero

Similar to normal Hollows, exploration within Hollow Zero also manifests as Bangboo being controlled around a Board.

But what's different is that Hollow Zero is divided up into four different areas based on how deep into the Hollow you are: the Edge, Interior, Heartland, and Core - each with several floors for you to explore. Defeat the enemies at the end of each floor to complete its exploration.

The exit on the final floor has a Final Threat. Clear it to complete the exploration of the whole area.

Combat & Exploration Effect: Resonia

The combat-enhancing effect (buff) you will get throughout a stage is called Resonia. Now for this one, it's similar to Honkai: Star Rail's Simulated Universe Blessings. Sorry for all the cross-game references, but it's easier that way for the explanation (and possibly many readers since those 2 games are quite famous).

  • Resonia comes in many types: General, Critical, Energy, Dodge, and more.

When you have 4 or 8 Resonia from the same category, an extra advanced Resonium will be generated. You can check this by looking at the bottom of each Resonia 'Already Owned: 00 Card.' Once you reach 4 Cards, you will automatically get the bonus buff.

Open up your Resonium Inventory on the left to view all the Resonia you own, as well as their effects.

Rewards for Hollow Zero

  • Every floor cleared while exploring Hollow Zero will give you Etheric Matter samples.
  • Even if you fail to defeat the final enemy, you will still get a certain ratio of Etheric Matter samples.
  • During the investigation period, you can claim investigation rewards based on the number of Etheric Matter samples collected.
  • Upgrade your Inter-Knot Level to increase the maximum number of Etheric Matter samples that can be collected within a given period, and unlock investigation rewards such as more Slots.

A content creator for HoYoverse games, focusing on Genshin Impact and Honkai Star: Rail.

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