There are seven Gnosis, each representing one of the world's seven elements: Hydro, Anemo, Dendro, Electro, Geo, Pyro, and Cryo.
There are seven Heavenly Principles Cards, each revealing one of the seven powers of the Heavenly Principles: reason, life, death, space, time, spirit, and consciousness.
Xing Yuan transmigrated to Teyvat and obtained the Genius Invokation TCG King System. No matter who his opponent was, the only way they could fight him was through a card game.
The price, however, was that his life had already begun counting down. Only by collecting the Heavenly Principles Cards could he defy fate and extend his life.
For the sake of the cards, Xing Yuan set off on a pilgrimage across the seven nations. And so began the tale of an undefeated god of war obsessed with card games, adventuring in Teyvat.
"I'll seal you inside a statue of the Seven," Raiden Shogun declared.
"Who cares about the Raiden Shogun or the Musou no Hitotachi? Beat me at cards first!" Xing Yuan replied.
I prefer playing cards, I think this book is pretty good