Beasts are exactly what it says on the tin: the wild creatures of the woods that dont quite fit into the usual archetypes (Bears, Ox, etc.)
Brightcap Badger and Infested Thrinax each promote overwhelming your opponent with saprolings and the more of them you have, the more powerful these cards are
If you are already familiar with what Ravnica: Clue Edition is all about, you can skip ahead to the Collecting section
For nine generic mana you get a 9/9 flying creature Saga that destroys a couple nonland permanents, draws two cards, and deals massive amounts of damage to your opponents' faces over the course of four turns
Similarly, any as [this permanent] enters the battlefield or [this permanent] enters the battlefield with abilities that the token has copied will also work
The price is also heavily tied to the specific artifacts on the bonus sheet within