Henry was marooned on a remote island with nothing but a soccer ball to keep him company for several years. He was eventually found and rescued by his boss. Grateful to the boss, he and the soccer ball now work at the island aquarium. The soccer ball is now Henry's manager, which has put an awkward tension on their friendship.
Each mastery level adds another card to the cardpool for defeating Henry. Each of the bronze, silver, and gold mastery levels unlocks a new card, while it takes all three diamond and onyx levels to unlock a single card.