I really want to write this Upper MG series where the plot for each book is kind of similar. All the main antagonists will be the planets personified. Basically, they hatched out of the planets as if the planets were eggs.

Each book will feature a different monster who hatched out of one of the seven planets (excluding Earth). I'm worried though, that this will get too repetitive. Like the readers will already know what's going to happen in each book. I think that in Lower MG you can do this, make the plots similar, but can you do this for sure in Upper MG without it getting repetitive?