Aria Blaze a defeated siren, with mauve fur, a purple and aquamarine mane, and violet eyes goes through a magic mirror that's really a portal? Sonata Dusk, another defeated siren, with ice blue fur, a turquoise and navy blue mane, and cerise eyes, and Rainbow Dash, a cyan pegasus with a rainbow colored mane and cerise eyes, are her sidekicks.
Together these ponies are finding and putting a stop to a major threat that can destroy Equestria.