>>720177548
It couldn't create a black hole.
Realistically, the only way to compress mass enough to form a black hole is for the mass to collapse under its own gravity. Any material in the universe (and anything containing it) would just be obliterated long before any physical force got close to crushing its atoms.
The cube, and any other object small enough to be pushed through a portal, is also a completely insignificant amount of mass and even if you could somehow compress it beyond its Schwarzschild radius (for a 10kg cube this is an area one billion times smaller than electron) the black hole would evaporate instantly.
To compress the entire Earth into a black hole, roughly one billion trillion (10^24) times more massive than the cube, it would have to be crushed small enough to fit on the tip of your finger.
