Outside of their exploits in Equestria Girls, we didn't get a whole lot of information on the sirens from the Equestrian perspective. Here's to hoping Sonata Dusk stays cute. Best seapony thing.
Sirens will arrive 3rd once April's FIEND series begins. Get the synopsis and stuff the break! And get the full Fiendship is Magic series over here.
Writer: Ted Anderson
Artist: Agnes Garbowska
Cover Artists: Amy Mebberson / Sara Richard
Synopsis: The Sirens from Rainbow Rocks Equestria origin revealed!Release Date: 4/15/2015
Thanks to Masem and Raul for sending it!