So I have the Spring, Summer, and Autumn Sphinx Relief's. I know that I have them for a reason but I can't exactly remember what. I do know they can be opened, I've done that for the books. I also know there's a hidden item that when you open you select a certain item and solve some riddle to get it. BUT I feel like there's a 3 use for these. I'm thinking it's something where we'll need all 4 Sphinx Relief's but again I'm not 100%.

Does any of this make sense, can anyone help clarify? Thanks.

It's been hinted at that there's gonna be something to the riddles in the books. We just need winter. No one knows for sure though.

There's a riddle in each season, where if you complete what's asked, with the item in your inventory, you get a different item. There's also a partial riddle in the descriptions of each of the books, and once winter comes out that will be solvable as well but we don't really have more information other than the fact that there is a 4-part riddle.