The Collector's Edition of Destiny 2: Shadowkeep contains a physical collector's item known as a Hive Cryptoglyph. It's a red cylinder with Hive runes on it, modeled after an item in the game that all players will be interacting with in order to craft gear in Destiny 2: Shadowkeep. But the replica that comes in the Collector's Edition of the Shadowkeep expansion contains a secret.
If the correct sequence of runes is selected on the Cryptoglyph, it will slide open to reveal a code and a URL to a page on Bungie.net. It is unknown at this time exactly what the code will unlock, but it looks to be completely exclusive to owners of the Collector's Edition of Shadowkeep.
A fan who goes by "soapcracker" on Reddit received his Collector's Edition early and solved the puzzle revealing how to solve the Cryptoglyph and showing what's inside. Some other people have also gotten their Collector's Edition and have also solved it revealing some more information about it.
First, to open the Cryptoglyph, enter this exact rune sequence by turning the different rows:
Inside the Cryptoglyph is a card that leads to one of two URLs that fans have discovered so far, either Bungie.net/hope or Bungie.net/dust.
Currently, these URLs redirect to a holding page saying to return on October 1, 2019, the day that Shadowkeep releases.
It's likely that this will unlock an emblem exclusive to owners of the Collector's Edition, but it could be something else entirely. It looks like whatever it is, these will be one-time use codes. Conversely, back when The Taken King released in Destiny 1, there were similar secrets found in the journal of The Taken King Collector's Edition but what ended up being an emblem code in the journal could be used by anyone and was shared online where any player could find it. Whatever this code from Shadowkeep's Collector's Edition unlocks, players have to wait until October 1st to find out.
The Collector's Edition is completely sold out so there is no way for people to get their hands on one at this point unless they win one from various contests some streamers and content creators are holding.
Destiny 2: Shadowkeep releases October 1, 2019 for PC, PS4, and Xbox One, with a Stadia version also in development.
Source: Reddit