Sonic x Shadow Generations combines two games: Sonic Generations, where players can enjoy speed-running various stages with Classic Sonic and Modern Sonic, enhanced with new elements, and "Shadow Generations," a completely new game featuring the dark hero Shadow racing through dynamic environments. The story begins as a mysterious creature called the "Time Eater" creates distortions in time and space, setting off separate adventures for Sonic and Shadow. Players can look forward to a high-speed action-adventure with distinct gameplay experiences and narratives.