It was around 2010 when i watched it but translated cartoons was arriving kinda late to my country (poland) so keep that in mind. I'm not sure if it was the main plot of the cartoon but they was collecting some kind of gems and puting them in sockets located in book cover. And when they put all gems in sockets a final socket in the middle of the cover opened. Unfortunately that's all i remember but i hope someone knows what cartoon it is. I'm looking for it for 5+ years now and i'm getting desperate haha

It was around 2010 when I watched it but translated cartoons was arriving kinda late to my country (Poland) so keep that in mind. I'm not sure if it was the main plot of the cartoon but they were collecting some kind of gems and puting them in sockets located in the book cover. And when they put all gems in sockets a final socket in the middle of the cover opened.