Black StoneInstall a bookshelf in your residence and interact with it to obtain Knowledge in many categories. 

It takes an hour of reading to obtain Knowledge from a bookshelf. You can continue interactin with a bookshelf (reading) even when you switch characters via Character Selection. However, disconnecting or changing server will end interaction.

You can obtain Knowledge from one of the many diverse categories available when you completely finish reading.  

There is a chance to obtain Knowledge you already possess. (Bookshelf durability is still consumed in this instance.) 

Although you cannot obtain more Knowledge through interacting with a bookshelf whose durability is at zero, the furniture you installed does not disappear. 

Rules for obtaining Knowledge from Bookshelves (Pearl Shop Item) are as follows:  

• A Knowledge category is determined according to an equal probability when reading from the chosen Bookshelf, is complete.  

• After the category has been selected, a specific Knowledge from within that category to be learned will be determined according to an equal probability as well. 

• If the determined Knowledge is an Ecology type, the Knowledge grade is also determined at random according to an equal probability. (S, A+, A, B, C)  

Accordingly, the probability of obtaining a Knowledge entry by interacting with a bookshelf is equal to (1 out of the total number of Knowledge categories) * (1/total number of Knowledges in the category determined). For Ecology type Knowledge, the grade of the Knowledge is determined based on the probability of (1/total number of grades).  

- There are a total of 183 Knowledge categories and a total of 2682 Knowledge entries within these categories that appear on the Bookshelves. (Last updated on Dec 8, 2021)  

- The probability of obtaining a certain grade of Knowledge is subject to change when Knowledge entries are added through an update.  

◈ List of Bookshelves (Pearl Item Shop) 

This list includes items you can only purchase during event periods.  

◈ Obtainable Knowledge from Bookshelves (Pearl Shop Item) 

• You can more conveniently find the Knowledge entry you seek by pressing Ctrl + F.  

• The grade (S, A+, A, B, C) of your Ecology Knowledge is determined according to an equal probability. 

• Percentages were only written out to the fourth decimal place. (Rounded from the fifth decimal place)