As you can see from the artwork here, all four in each set are a variant of a theme, with a creature from the game looking over the land around them in a particular kind of season
If you want some inspiration for meta decks, tournament successful lists, or wanna see different strategies, look at the completed results from a recent Late Night Event here: You can import a deck from one of those events by copying it to your clipboard and pasting it right into PTCG Live
To add to the, uh, mystery, there are two versions of Mystery Booster a Convention Edition that will be available at MagicFests and conventions moving forward, including PAX Unplugged in Philadelphia, Dec
The ideas initially were rejected mostly because they would be too hard to implement or track in paper, but in a digital environment, these ideas could have a second chance
Or you can pull them off for two mana to make a land a 2/2 for the turn and then put a +1/+1 counter on it so it'll be a 3/3 this turn and then could grow in future turns as you do this again