Replying...
Intro. Two similar universes get merged together by the System. The System is a powerful program that uses magic to operate. Earth and it's universe, as well as the other planet, Sol-III (the third planet from the sun), and it's universe, are both old enough to qualify for system integration, as well as with enough empty space to be combined with another. The System chose these two planes of existence to combine into one. Double the people, double the space, with magic and the System included. The System giving every person access to a LITRPG gaming RPG system, a set of screens and windows that allow them to get stronger like an rpg game, but with extra abilities, skills, and classes for people who aren't going to be combat oriented. The magic and merge causes natural animals to mutate into monsters, and new ones to spawn out of ambient mana.

System World Merge

@James