>>50345390The only egg we know of actually being produced in game is the one made by Arceus in HGSS with the help of Unown. This egg can produce Dialga, Palkia, or Giratina depending on where you stand. The Unown cannot breed and are presumably the instructions, genetic coding language, etc. that Arceus uses to generate the laws in the Pokémon universe. Unown plays a very significant role in Hisui/Sinnoh, with these Pokémon only appearing in those regional dexes and Johto, the one that introduced Unown in the first place. The Solaceon Ruins, where Unown can be found and the message in those games about “All lives touch other lives to create something anew and alive,” is connected back to Unown and to Sinnoh/Hisui’s mythology.
My guess is that Arceus, the true Arceus that we see at the beginning of Legends, is the one in charge of the Pokémon multiverse, and Unown were created as the letters and instructions so that other life can be created. Unown cannot breed yet they are produced in abundance. The Unown “A” is found in the Diamond Settlement, after you complete the Solaceon quest; both are in. The Crimson Mirelands. The Unown “?” is located behind your house, since you lost your memories and have many questions.
Game Freak wouldn’t create something like the Arceus mythos and connect it then to Arceus unless that was the intent.