But then the peace was shattered when evil Queen Beryl found a way to break out of her Negaverse to their universe, she attacked the Moon Kingdom with a vengence. Queen Serenity defeated Queen Beryl's strongest warriors and locked them inside her Imperial Silver Crystal and sent them to earth. The Moon Kingdom was forever distroyed, with her power broken, Queen Serenity used the last of her strength to send Princess Serenity and her court to a new future on earth.
The Sailor Scouts were all princesses of their own respective planets, but also a part of Serena's court. Luna and Artemis were sent to be their gardians and to reunite them. But if the Negaverse did show up again, Queen Serenity made sure they can activate the Sailor Scouts to fight off any new threat by Queen Beryl.