More often than not, Rare and Mythic Rare cards are the chase cards of a set, but not every Rare and Mythic Rare is expensive
Each color in Magic has its own subset of lords or anthem effects that boost specifically creatures of that color
Maybe this is another card with the Gift mechanic, and the number of cards you get to look at when your Hideaway card enters is determined by whether you promised a gift or not
You get Scar, Vengeful Lion and Kronk, Head of Security, both playing different roles in the deck
Clean condition
So, if you have all ten color pairs in your cube, you'd probably want to be consistent and include a land (for example, a shock land, fetch land, or check land) for each