The Emerald is a crossover 3D adventure game. It is for the Wii U and rated E10+.
NOTE:The story is short. OTHER NOTE:This is a summary.
Mario and some other characters find two emeralds on the ground in a city park. Then they get the power in the emerald, making them the emerald heroes. Basically, the rest of the story is unlocking characters and fighting the character's antagonists.
There are many playable characters.