Sky key (an end game novel) - James frey & Nils Johnson-Shelton

In the world of Endgame, twelve ancient and powerful families have been secretly preparing for centuries for a cataclysmic event known as The Calling, where their descendants must fight to the death in a contest to determine the future of humanity. These families are referred to as the Players, and each of them is trained from birth to be part of this high-stakes battle for survival and dominance. The ultimate prize for winning Endgame is control over the future of the human race.

In the first book, the Players are thrust into a global game where they must solve complex puzzles, complete dangerous tasks, and engage in brutal physical and mental challenges to outwit and outlast each other. The competition is deadly, with alliances forming and breaking as the game progresses.

"Sky Key" picks up with the remaining players continuing their struggle to find pieces of the Sky Key, a mysterious artifact tied to the ultimate power of the game. The key is essential for unlocking the final stage of the Endgame, and whoever controls it will gain an overwhelming advantage. The story focuses on the quest to obtain the Sky Key, which is rumored to unlock the power to either save or destroy the world, depending on how it is used.