Marilyn

"Guh! Guhhhhh?"

- Marilyn

Marilyn is one of the three Shadow Sirens and the middle sister of the older Beldam and the younger Vivian (which was later on replaced with Doopliss). She and her sisters worked alonside the Secret Society of X-Nauts to find the seven Crystal Stars and open the Thousand-Year Door. Marilyn and her teammates appeared several times throughout Mario's adventure in Paper Mario: The Thousand-Year Door, making numerous attempts to show him and his partners down and hinder their progress.

Plans and Operations
Many years prior to the events that took place in the game, Marilyn and her sisters were servants of the Shadow Queen, an evil demon that once threw the world into the depths of terror and sank the entire town of Rogueport underground. After she had gotten defeated and sealed by the four heroes, the Shadow Sirens started devising a plan to gather the Crystal Stars and break the seal on the Thousand-Year Door, so that they could serve their queen once more.

During their search, Marilyn and her teammates eventually came across the extraterretrial organization known as the Secret Society of X-Nauts. They soon got acquainted with their leader, Sir Grodus; they then joined him and got enlisted in his services, pretending to be nothing more than hired help. Knowing how desperate he was to rule the world, the Shadow Sirens told Grodus a lie, saying that the Shadow Queen would obey his every command if he's to release her. They also told Grodus about the seven Crystal Stars, which were required to break the Thousand-Year Door's seal. Along with that, they also informed him about the Magical Map, which was contained inside of a treasure chest that could only be opened by one who's pure of heart. Neither Grodus or the Shadow Sirens could open the chest themselves because of their evil and tainted ambitions, so they decided to get someone else to open it for them. That "someone else" just-so-happened to be Princess Peach.

Boggly Woods
After Beldam's failed attempt to abduct Princess Peach and steal the map from her after the chest was opened (due to the fact that there were many witnesses around), she had no choice but to flee and return to the base. Sometime later, after Mario and his partners defeated Hooktail and obtained the Diamond Star, an X-Naut soldier informed Grodus of this, and sent the Shadow Sirens on a mission to ambush Mario at Boggly Woods and steal the map from him. Before then, Grodus gave them a sketch of Mario so they will know what he looks like when they come across him. Unfortunately, Beldam somehow managed to lose that sketch, and as a result, none of the Shadow Sirens recognized Mario when they came across him. None of them except for Marilyn, that is. However, this is one of the rare instances in which Beldam could not understand a word she was saying, so she ignored her, and continued yelling at Vivian, which she was blaming for losing the sketch that was given to them. Eventually, they managed to find the sketch, and recognized Mario as soon as he and his partners returned to get necklace that Beldam took from Vivian, which belonged to Flurrie. The Shadow Sirens (including Marilyn, making this the only time she spoke in the game) introduced themselves to Mario and company, and revealed their intention to steal the magical map from them so they could obtain the rest of the Crystal Stars. Shortly afterward, the Shadow Sirens engaged Mario and his associates in combat and were eventually defeated. Beldam then blamed their defeat on both Marilyn and Vivian, telling them to "prepare for a world-class punishment session when [they] get home". After that, the Shadow Sirens fled and returned to the X-Naut fortress, leaving the necklace behind in the process.

Twilight Town
Later on, up at the X-Naut Fortress, Grodus ridiculed the Shadow Sirens for their failure to steal the map from Mario, but Beldam then told him about the Superbombomb, a weapon that she prepared that would bring Mario to a "quick and certain end". Although Grodus was displeased with their previous failures and was beginning to lose his patience, he still trusted Beldam's word, and sent the Shadow Sirens to Twilight Town, Mario and company's next destination. Before they could use the Superbombomb, however, Beldam ended up losing that, too, just as she did with the sketch, and once again blamed Vivian for it. After that, Vivian was left to search for it while she and Marilyn go to take a "well-earned siesta". After they finished their nap, Marilyn and Beldam found that Vivian was no longer there (as she had recently joined Mario's party). After that, Doopliss, who was just defeated by Mario and Vivian, came rushing by, and was soon recruited as a new member of the Shadow Sirens, and thus a new member of the Secret Society of X-Nauts, as well.

Poshley Heights and the Palace of Shadow
Marilyn was not seen again until Chapter 6, when Mario and his partners arrived at Poshley Heights. She, along with Beldam and Doopliss, were seen at Poshley Sanctum stealing what was thought to be the Garnet Star. After stealing it, the Shadow Sirens fled from the scene. Mario and his partners were about to chase them, but Pennington, the Sactum Manager, told them that the "Crystal Star" they stole was a fake, and that the real one was cleverly hidden somewhere within the Sanctum.

By the time Mario and his partners reach the Palace of Shadow, they confronted the Shadow Sirens again. Beldam then revealed to them that they were tricked into opening the Thousand-Year Door by Doopliss, which was disguised as Professor Frankly. As it turns out, they managed to abduct the professor sometime during the events of Chapter 7, and had him stuffed in a closet somewhere. After that, the Shadow Sirens engaged Mario and his allies in combat once more, and ended up suffering another defeat.

Sometime later, after Mario and company managed to defeat Bowser and Kammy Koopa, who literally "dropped in" unexpectedly after Grodus' defeat, Grodus somehow regained consciousness and took Princess Peach down to the Shadow Queen's resting place. Grodus told Mario and company his motive for kidnapping Peach, declared himself the ruler of the world, and released the Shadow Queen, which managed to cover the world in darkness by her mere presence. Grodus presented Peach to the Shadow Queen so that she could be used as a vessel for her spirit. After the Shadow Queen possessed Peach's body, Grodus orders her to destroy Mario and company, but she refuses, and instead blasts Grodus to pieces, stating that she takes orders from no one. After the second strike to Grodus' head, the Shadow Sirens appeared and explained to the Shadow Queen that they were the ones truly responsible for reviving her. The Shadow Queen congratulated them for the work, and then offered Mario and his allies a chance to join her. They, of course, refused, and engaged her in combat. They eventually managed to defeat the demon with the power of the Crystal Stars, Princess Peach, and the wishes of all their friends. After the Shadow Queen was defeated, Beldam, Marilyn, and Doopliss retreated.

After the Shadow Queen was defeated, Beldam and Marilyn changed their evil ways, and decided to make ammends with their sister. Beldam apologized to Vivian, promising to never mistreat her again, and three of them now live peacefully in Twilight Town.

Super Paper Mario
Although she didn't physically or visually appear in Super Paper Mario, she and Beldam were still mentioned in Vivian's Catch Card description.

Personality
Marilyn, unlike her teammates, happens to be very quiet, and is never or rarely ever seen talking. The only words she has ever spoken throughout the entire course of the game were, "The Three..." while she and her sisters were introducing themselves to Mario and company. Otherwise, she'll usually make "Guh" sounds, and other variations of it. Despite the fact that she usually does not talk in plain, understandable English, Beldam usually understands what she's saying, or at least trying to say anyway.

Although she has a very dark, mysterious personality, Marilyn has still been shown to be very loyal to her sister, as she will usually follow whatever orders are given to her, without question. It was also revealed that Marilyn happened to be the "favorite" of the group, as Beldam would treat every other member of the Shadow Sirens with as little respect as possible.

Powers and Abilities
Marilyn stands out and has proven herself to be the strongest member of the Shadow Sirens. She happens to psychically strong and specializes in powerful lightning magic abilities. Mariln also has the ability to charge her attack power various times, and if the player does not stop her, then she could double, or maybe even triple her already-high attack power, which may even cause an instant death. As with her sisters, Marilyn knows how to use the Veil ability, where she could sink into the shadows. This ability could either be used to hide or teleport, as the cutscenes have demonstrated. Similar to Beldam, Marilyn was never seen using this ability in battle.

Trivia

 * Marilyn is the second character in the Mario series (with Mario being the first) to be described as the "strong, silent type".
 * The color of her hat represents the power she has over the thunder element.