What secret stone did Valkyria use in Doomsday City?

Valkyria, the city of doom, uses fire to make secret stones.

Doomsday City is a role-playing mobile game developed by Dong Hao Network. It tells the story of human beings cooperating and using each other in order to survive in the last days full of zombies.

Doomsday City is a survival role-playing mobile game that combines classic round fighting, exploration, card cultivation, management, puzzle solving and other elements. In the game, the protagonist leads his partners through difficult adventures and successfully finds the abandoned hotel. Based on this, he constantly explores new unknown areas, constantly accepts new powerful companions, constantly expands the activity area, looks for lost relatives and explores the truth of the world.