Each player picks the one that is most convenient for them
That's the sort of self-sufficiency one would expect from Squirrels rather than a bat
However, despite the lack of dragon cards, it has plenty of potential since it can repeat this effect as long as you keep drawing dragons
There are tons of these in the game, multiples in each set, and most people probably think of these when they think of a cycle
The way it works, is when Thassas Oracle enters the battlefield, you get to look at the top X cards of your library, where X is equal to your devotion to blue (how many blue mana symbols appear in the casting cost of all permanents you control)
Im all too used to playing games that take 20-30 minutes to review the instructions for the first time and set up the board