The information here comes from a post made by the official account on Hoyolab on 30 January 2024.

“For people who spend their lives in the desert, the fleeting memory of aquatic life is priceless.”

We're about to arrive at Penacony, the Planet of Festivities!
This once-in-an-Amber Era event, Charmony Festival, is near at hand. Many organizations throughout the cosmos have been invited to attend, and the messenger from the Garden of Recollection is one of the honored guests too.
Pom-Pom heard that the Trailblazers don't know a lot about the Garden of Recollection? Don't worry. Pom-Pom will tell you right away~

— Pom-Pom

Based on what Pom-Pom knows, Memokeepers from the Garden of Recollection believe reality and imagination to be a myth. Even stars die and black holes evaporate. On a cosmic scale, they vanish in a breath. In this flood of time, the only treasure is the memory that proves the existence of people.

Memokeepers from the Garden of Recollection are dedicated to preserving and sharing memories. Enlightened by their master Fuli, Memokeepers shed their mortal flesh and live on as memetic entities. With this unique gift, they can freely traverse between worlds, unconstrained by physical limits.