There are two types of book delves (潜書, sensho).
When you click on the Tainted Book or the Sealed Library icon, it brings you into the world of a tainted book where you must vanquish various types of tainted creatures in order to successfully cleanse the book.
Tainted Book Delve
Once you click on the Tainted Book (有碍書, yuugaisho) icon, you will enter this panel where you will see lots of books.
These books are sorted into the i-ro-ha [いろは] sequence, which is a traditional ordering of the Japanese syllabary, a system similar to 'ABC'. The wiki will be using i-ro-ha [いろは] as reference to the various combat stages within a series of books.
The first series is the i-series [い], with the first book named as i-1 [い-1]. You may select different books to cleanse by clicking on the i-ro-ha [いろは] tabs on the left, clicking on a book's spine, and then by choosing a team, you may delve from the Delve (潜書) button on bottom right corner.
Each book has its unique taints and recommended element (displayed on the top-right corner of the book with an elemental sign) you should consider when forming teams in Formation and choosing a team for the delve. You can obtain more information in the Tainted Books, where a full list of the books may be found.
Once you enter a tainted book, your party will meet with different types of tainted monsters. You can obtain more information of them by accessing the Taint Types section.
The battles consist of three waves, and usually the last book (fourth book) of each shelf have a bigger taint in last wave of the delve, which is considered the "boss" taint. To bring down the taints, your writers will execute different kind of attacks depending on their status. Some of these status effects usually trigger when the "corrosion value" (also known as HP) of a writer drops too low or they've been attacked on a long run to fill their Epiphany Gauge. More info of the game's combat mechanics can be found here.
Upon complete purifying of the tainted book, you will be rewarded the writer of the book (do note that this is a reward for clearing the book for the first time only). List of all writers can be found here.
Auto-Delve (自動潜書) becomes available once you have cleared the first book of the i-shelf (i-1). Writers will go patroll in the books automatically, and through time gather items like Alchemy Thread (), different kind of souls () and Soul Gears (). The further you advance in the shelves and purify books, the bigger amount and rarer items you may acquire through the auto-delve.
You may claim the auto-delve rewards by pressing the yellow button Receive Report (報告を受ける) on the right side of the screen. The longer you wait and let your writers patroll, the more items you get and likely gain some rare items.
※ Please do note that auto-delve hits limit after 24 hours since the last claimed report!
You must claim the auto-delve rewards at least every 24 hours or few times a day for efficient resource gathering as you can't gain more than items worth of 24 hours at a time. If your auto-delve has hit the resource limit, the golden bookmark will have text Patrolling Complete (巡回完了) and there will appear a green banner Resource Limit Met (素材上限到達) above the receive report button.
Sealed Library is unavailable from 2021/07/28 to 2021/08/30 due to changes that need to be made to the books to fit the new delving system brought along with the July 28th big update.
Sealed Library (封蔵書, fuuzousho) is another section of Tainted Book with similar game mechanism, introduced during the Purify "Alice's Adventures in Wonderland" event as part of the Foreign Secret Records storyline, which acts as a part of the game's Main Story. The Sealed Library can be accessed once you have reached player level 3.
Once you click on the "Sealed Library" icon, you will enter this panel.
Books are sorted into shelves following the Latin alphabet and divided into chapters, which consist of multiple paragraphs for cleansing. The first series is the A-series, with the first chapter named as A-1, and its first paragraph being A-1-1.
Most of the Sealed Library's mechanism is the same as that of the Tainted Books, with the introduction of raid bosses. During the first runs of A-3-5 and A-4-5, players will encounter bosses with huge amount of HP and be expected to defeat them by draining their HP through multiple delving attempts.
A full list of all available Sealed Books can be found here.
Equipment Book Delve
- Click on the open slot to open up the writer's list. This is where you can select a specific writer to delve into the book. Your library assistant will not be included in this list, so if you want to use them to delve into equipment books, you must change your assistant in the office.
- Choose your selected writer by clicking on his tab.
Once your writer is selected, you will see the amount of Equipment Books and Governors (調速機) you have. Once you click the Confirm button, the delving will immediately begin. For delves without the use of governors, a timer will appear. The higher timer, the more likely your result will be a rare writer or some equipment (outfit or memoria card).
If you change your mind and want to obtain your writer or equipment immediately, click on the governor icon to use a governor, which will instantly finish the delve.
See more info of Equipment Books and the timers here.