Astrologers playing cards
Astrology themed pack of playing cards, that gives an advantage to those who know a bit about the sky.
Each suit is related to a different astrological entity, for example stars are diamonds, hearts are moons, and so on. On the back of each card is written the name of what appears on the front. So if you read "Orion's Belt" on the back, you'd know that there would be 3 stars on the back and therefore your opponent would have the 3 or diamonds.