Humanity
Indigo has a strange habit of accidentally running into aliens. (Universe consists of a regular Earth with the existence of other planets - Kelleia, Aria's planet, +more.)
Sci-fi
A few other planets have had access to Earth, unbeknownst to Earth of course, but none have revealed themselves. Earth finally reaches a level of technology where they are able to go farther into space and discover another planet that is very similar, and the first thing Earth does is try to take it over. This new planet, Kelleia, is peaceful and a bit behind Earth, they had no awareness of other planets. They also had a very peaceful culture and society and only had one army for the whole planet. So they fight back with their solitary military and send spies to live on Earth and figure out its weaknesses and soft spots. (This is where story starts, before this is background). Once they've gathered enough information, they attack the people...subtly first, with awful and immoral personal attacks and spreading and causing horrible news to break them down. Then they announce what's been going on and the war truly begins.
World broadcasting, new weapons, updated space tech - Earth, alien tech - from Aria's and Kelleia
Normal
Earth and Kelleia have no magic, but some other planets do and they are all different. Aria's planet allowed for minor shape shifting.