Since Exocross allows Guest Teams, I'm going to explain, what exactly they are.
A Guest Team is a team, that already existed before their members joined Exocross.
Guest Teams join, because they want to prepare for coming wars, or just want to duel other teams.
Guest Teams can be challenged by anyone. You just have to tell one of the site admins, that you're going to have a war.
You HAVE to wait for a confirmation from an admin, before you can start warring.
Dueling a Guest Team is rewarded.
The winning team (Guest or Intern), wins 50 points for their respective team.
Have fun dueling!