Sirenoid is an villainess-turned-heroine from Bakugan Battle Brawlers, as well as one of the supporting characters from Bakugan New Vestroia.
Sirenoid is a mermaid-like Bakugan wielding a magical lyre to soothe souls. Sirenoid creates a forceful wave to boost its power and destroy its opponents. It uses its dolphin-like tail for speed and mobility.
Bakugan Battle Brawlers
Sirenoid shares a special relationship with her partner Klaus Von Hertzon. She wears a long, flowing robe and protects herself with the harp she carries. Sirenoid is mostly based on Sirens that lure in sailors by looks or by any devious way like how Sirenoid uses a harp. She is in love with her master Klaus Von Hertzon and when she is living in Vestal, she lives in the fish tank of Klaus' office, albeit in her open Bakugan sphere form. This is referencing the fact that she is an Aquos Bakugan. Aquos Sirenoid shares a close bond with her master brawler, Klaus Von Hertzon. Whenever she loses a battle she asks him to forgive her.
When Preyas first saw Sirenoid, he thought she was beautiful. With the help of the Ability Card Anthemusa, she sent Preyas to the Doom Dimension, as well as Marucho's Limulus and Juggernoid. She then battles alongside Fourtress and Tentaclear against Drago, Tigrerra, and later Preyas, but was defeated when Drago evolved. She sent Dan's Griffon to the Doom Dimension. While under the influence of negative energy from the Silent Core, her personality was very vicious but after being freed from it, she appeared more calm and caring. She is then sent to the Doom Dimension after being defeated by a newly evolved Hydranoid.
Sirenoid came back to Klaus after the Legendary Soldiers of Vestroia sent all of the Bakugan from the Doom Dimension back to Earth. After Sirenoid is retrieved, Klaus battles Alice when she comes to his castle. Sirenoid wants to defeat her very badly, calling her a coward when she refuses to fight, even though Klaus and Sirenoid win anyway, though she could have been acting to help Klaus motivate Alice as she acted calm the next time she saw her. She later assists in stopping the Doom Beings by taking on both Hairadee and Druman, attacking them with Forcing Wave, though she wins after being pumped up by the Silent Core she quickly loses in a rematch. She later assists in battling Rabeeder with Alpha Hydranoid and Juggernoid but lost when Rabeeder used Terra Crunch. She then helped most of the other brawlers in battling the remaining Dooming Beings.
Bakugan: New Vestroia
Sirenoid is seen in Invasion of the Vestals playing her harp before the Vexos capture all the Bakugan. After being freed, she is seen playing her harp again, while watching the Resistance go their separate ways.
In Reunion, Sirenoid is seen again playing her harp.
In Saved by the Siren, Sirenoid later rejoins Klaus when he goes to Vestal and aid's in Ace's defeat of Mylene. When Klaus congratulates her on her victory, she blushes in a bashful fashion. For some reason, Klaus keeps Sirenoid in a fish bowl. She also acts as Klaus' secretary, informing him of any meetings and events he must attend to during the day.