Murid, also known as the "Dream Princess", is a princessly doll-like Youma/Negemonster and one of the many villains in the Sailor Moon universe.
Queen Beryl was irritated at Jadeite as she learnt from him that Sailor Mars has joined Sailor Moon and Sailor Mercury in their fight towards her Dark Kingdom and Queen Metallia. In response, Jadeite hoped to trap the trio in an amusement park called Dream Land. The amusement park which recently opened was plagued by problems with fifty people disappearing since it opened. Ami Mizuno recommended that Usagi, Rei and she go there as life indoors was driving them crazy. This was shown by the constant bickering between Rei and Usagi over a Sailor V movie. Ami also hypothesised evil activity, so the trio went over there to investigate.
As part of his trap, Jadeite summoned his youma Murido to gather energy from those who attended the amusement park so as to awaken Queen Metalia. Murido masqueraded as the Dream Princess, the mascot of Dream Land. As the Dream Princess, Murido kept the visitors of the amusement park entertained with rides, and mechanical animals controlled by an apple she held with her hand. She also hosted a party at the park's Sweet Dream Factory, to which she invited all the parks guests. When guests arrived at the house, they were lured with various sweets. Once Murido questioned the guests to whether or not they were enjoying themselves, she blew from her mouth a red mist which caused the visitors to hallucinate and enter a dream state where, the Negamonster stole their energy for Jadeite via the apple she was holding. Usagi was enthralled by the Dream Princess, her mechanical animals and the amusements she offered, although Rei felt a strange aura surrounding her.
Whilst investigating the disappearances at the amusement park, Luna decided to split the trio up to investigate the amusement park more easily. Usagi and Rei paired off in one group whilst Ami and Luna paired off in the other group. To the detriment of the other group, Ami fell victim to Murido as she drained Ami's energy as well as some visitors during one of the Dream Princess's party at the Sweet Dream Factory. Rei realised something bad had happened inside the Sweet Dream Factory so she and Usagi transformed.
Sailor Mars blasted away at the locked door of the Sweet Dream Factory with her Fire Soul attack and pursued the Dream Princess. Once inside, they were confronted by the Dream Princess who blew her red mist at Sailor Moon and Sailor Mars. Both of them began to hallucinate, dreaming that they were in a field of flowers. The Dream Princess tried to offer Sailor Moon a wreath of flowers but that wreath turned into a snake that bit Sailor Mars on the arm as she knocked it away from Sailor Moon. Although the snake turned into stone, the venom from that snake was also turning Sailor Mars to stone but she freed herself from the effects of the venom by using her anti-evil scrolls (Akuryo Taisan). The effects of the hallucination wore off once the Dream Princess revealed to Sailor Moon and Sailor Mars her true youma form. Again, Murid caused Sailor Moon and Sailor Mars to hallucinate as they dream of being in the company of Tuxedo Mask. Completely off their guard, Murid was about to finish them off with her apple curse when the real Tuxedo Mask use his rose to knock away Murid's apple, thus stopping Sailor Moon and Sailor Mars from further hallucinations. Both Sailor Moon and Sailor Mars retreated as they realised that the youma was too powerful for them to attack alone. By chance, they found Ami who transformed into Sailor Mercury. Sailor Mercury used her Sabão Spray attack to create a fog and confuse the youma. Sailor Mars then used her anti-evil scrolls (Akuryo Taisan) to immobilise Murid and Sailor Moon and Sailor Mars combined their Moon Tiara and Fire Soul attack to finally destroy Murid. Jadeite wasn't pleased at this because now he has to inform Queen Beryl of the princess' destruction. Upon her defeat, the Sweet Dream Factory disappeared as well as the apple which trapped the stolen energy from the amusement park guests.