Humanity tore open a portal by accident.

The Elven world answered it with conquest.

Elves crossed into Earth, not as explorers, but as a unified military force. Human armies collapsed within months. Modern weapons proved ineffective against elven biology, coordination and magic. Governments dissolved. Resistance was erased. Billions died during pacification.

Desperate, humanity unleashed all its nuclear bombs across the entire world at the same time. Since the portal was still open, the explosions affected both the Earth and the Elven world. The massive explosions destroyed everything in their path.

The Elves, who had been so sure they would conquer Earth, were reduced to few due to their lack of proper defenses against such powerful weapons. Meanwhile, humans had bunkers, underground hideouts and spaceships that they used to survive. Now, the Elves were reduced to only a few.

The radiation left behind by the bombs made the world a place where only the strong could survive. Every day was a competition for resources. The city ruins are littered with burnt corpses and debris. Insects mutated into massive monsters that devoured anything they could catch. It wasn't weird to see something like a mutated roach eat something like an elephant and then get eaten by a mutated mantis only a second later nowadays.