All the magical trouble began when the Guardians sealed away the greatest darkness in the universe. They used their full power to seal the darkness away, and consequently sealed away themselves.
During Sunset's battle with Twilight, a large surge of magic spread through Canterlot. The magic caused the seal to weaken and the darkness started to escape. The Guardians woke up after their thousand year slumber and realized the seal had been weakened. They knew their true forms would destroy the darkness, but the city would follow. They used their combined energy to transfer their power to some humans. These humans gained new powers and enhanced abilities. Now it is up to them to destroy the darkness and save the world. They are the Power Rangers: Guardians!