469 is the Bonelord language. In written form 469 appears as a coded sequence of numbers lacking any punctuation or spacing within the text. Within the Hellgate Library you can find many books written in this language. Many people claim to have translated this strange language, but none have ever been able to supply any solid proof that supports their claims. Some of those who claim to have solved it say they do not think translating the books has a purpose. The code of numbers might mean nothing or it could just be too hard for the average Tibian to solve the mysteries of the 469 language.
There are also two books related to 469 in the Isle of the Kings Library. Shelf 21 contains Beware of the Bonelords (Book), which records information about the Bonelord race, such as their language and necromantic rituals. Shelf 39 contains a book that is written entirely in 469, like the books in the Hellgate Library.
See also Hellgate Library/Possible Solutions and A Wrinkled Bonelord/Transcripts.
In December 2013, Isoge from Celesta compiled many different sources into a working theory in this thread on Tibia.com. His theory suggests the use of real life number coding was used to create 469. For example, he used the dictionaries to decode 469 as meaning "Bonelord".