In Street Fighter X Tekken, the mysterious cube is called Pandora.
The object crash-lands in Antarctica and becomes the focal point of the crossover’s story. Researchers cannot determine its origin or purpose, but they discover that it reacts when people fight near it, releasing a water-like energy that appears to increase the combatants’ power.
That unusual reaction leads the characters to name the cube Pandora, invoking the mythological container associated with unleashing powerful and dangerous forces. The game’s story mode follows different teams as they pursue, investigate, or attempt to exploit the object.
Pandora is also connected to Pandora Mode, a gameplay mechanic in which a character sacrifices themselves to temporarily gain enhanced strength and abilities. It is not the Psycho Drive from Street Fighter lore, nor is it Ouroboros, a separate name associated with other fictional settings. The cube’s name is specifically Pandora.