The Shadow Sirens are one of Mario's enemies in Paper Mario: The Thousand-Year Door. They appear to serve Sir Grodus, but are really only loyal to the Shadow Queen. They confront Mario once in Boggly Woods, and again in Palace of Shadow with Upgraded moves, although Vivian has by now joined Mario's team, so she is replaced with Doopliss. With the Shadow Queen defeated, they are believed to have been disbanded, or at least have stopped committing evil deeds.
Beldam is the leader of the Shadow Sirens. She has the ability to control the element of ice, but isn't all to strong of a fighter. To make up for this, she is also able to power up other enemies, mainly Marilyn. She used to be incredibly cruel to the other members, mainly Vivian and Doopliss until her redemption at the end of the game.
Marilyn is the powerhouse of the Shadow Sirens. She controls the element of electricity, and is the strongest member of the Shadow Sirens, and has the most hit points. She is loyal to Beldam and never questions her. She never speaks except to say "The Three".
Vivian is considered to be the weakest of the Shadow Sirens. She has the ability to control the element of fire. She left the Shadow Sirens and joined Mario after taking too much abuse from Beldam. She was later replaced by Doopliss in The Shadow Sirens for joining Mario and his friends. In the Epilogue, she returned with her sisters, while they promised to never be mean to Vivian ever again.
Doopliss is Vivian's replacement. He is able copy the image and abilities of any person, mainly Mario. You fight him for the Ruby star in Creepy Steeple. Due to not being the same species as the other members, he can't travel through the shadows. During the Epilogue, he appears to have left the Shadow Sirens to perform alongside Madame Flurrie in a play based on Mario's adventures.