Template:InfoboxMotDSeiren (known as Amphibia in the English dub) is the eighth Cardian, whos name comes from the Italian word, "Sirena". Ail and An send her to gather energy for the Makaiju. She is a mermaid with pink hair that can extend and constrict enemies to drain their energy. She can also shoot blasts of water from her mouth, fly, and use a pollen powder that can put anyone who touches it to sleep. She appeared in Episode 8 of Sailor Moon R.
Ail and An summoned Seiren at T-A Girl's Academy's cultural festival after raising the audience's energy level when Sakurako Ougi convinced them to dress up as aliens for the fashion show. Seiren made everyone fall asleep with her powder but Usagi, Ami, Rei, Makoto, and Minako escape the attack. Seiren used her hair to drain Rei's energy but the others transformed and stopped her. Seiren began draining their energy but Rer transformes into Sailor Mars and stopped her attack with Fire Soul, however, this was not enough to destroy her. Just then, Moonlight Knight appeared and stopped Seiren's attack. When she swung her tail and knocked over the music that Rei worked so hard on, Sailor Mars used a new technique, Fire Soul Bird, to damage Seiren and restore the other Sailor Senshi's energy. Sailor Moon then destroyed Seiren with her scepter.
- Seiren could only repeat her name in the original version but in the English dub she is capable of speaking.
- In the original anime, she was voiced by Megumi Ogata. In the English dub, she was voiced by Alison Sealy-Smith.