Led by Mikeru in the second season of these series, they want to wipe out human kind who had purged their "beautiful planet" using the power of the Mermaid Princesses, the Panthalassa clam, and the power of the Ancient beings that lived before the time of the Mermaid Princesses and the Panthalassa clan.
Mikeru resembles an angel and is the one who launched a personal vendetta against the Mermaid Princesses after learning their relations with the human world. Although he is strong enough to resist any song the Mermaid Princesses would dish out against him until the finale, he is cursed with a weak body. He steals both Kaito's memories and Seira's heart in order to keep himself alive. In the manga, it is revealed that Mikeru is under the control of Fuku and is very good and gentle at heart. Mikeru is an ancient angel and is disgusted by what humans had done to the Earth that him and the other angels created. This explains why he needs Mikaru's body, Seira's heart, the heart of a mermaid princess, which means a fairly large amount of power, and Kaito's memories because he is a very powerful prince whose powers may rival those of the mermaid princesses. Mikeru believes that "angels" and mermaids are superior beings to humans because both species understand the importance of the Earth and each have powers, in one form or another.
Fuku appears like a super deformed angel with the head of a boy and the body of a bird. He's Michel's "right hand man", as well as his messenger to his servants, but at times orders around even Michel. He turns out to have a larger role later in the story.
The Great One
A spirit in the form of a flame atop of Michel's castle, he guards it for him. At one point, Fuku-chan claims that his words are Michel's words, and Michel's are That One's words, and That One's are God's words. He has a higher authority than Michel and has a strange relationship with Fuku-chan, where it is unclear who is in charge. During the final battle, it is revealed that he is, like Michel, a pawn.
Lady Bat calls himself "the wings of love and pleasure." Michel's vampire-like servant. His song hypnotizes the listeners into his spell so he could "bite" the person while they are asleep. There is certain controversy about his real gender, especially among fans in the West; in the manga, Lady Bat is actually a man wearing women-clothing. He is also strong enough to bring the Idol-form Princesses back into Mermaid-form. While in the manga Lady Bat identifies himself using feminine pronouns, in anime he uses the masculine pronoun "boku" Another difference is that in the manga he is about as tall as Mimi and his ponytail is shoulder length; while in the anime he is considerably taller (slightly taller than Lanhua) and his ponytail reaches the waist. Also, in some anime episodes, when concealing himself, he has worn male clothes. In his real form he has dark red hair and lavender-colored eyes; while in his human disguise form the hair is black and the eyes are greenish-blue.
Lanhua calls herself "the wings of desire and contentment." Michel's butterfly-like servant. She can divide into a dozen smaller versions of herself (which really do not look harmful or dangerous; in fact, very cute) to play a tune that makes the listeners dance until they die. She is called Ranfa and Lang Fa in some merchandise, but the English translators for the manga decided to follow the Mandarin Chinese pronunciation of her name. In her real form she has purple hair and red eyes, in her human disguise form the eyes are brown and the hair color is the same.
Alala calls herself "the wings of dreams and decadence." Michel's fairy-like servant. She's quite peppy and upbeat most of the time. She sings two songs in the anime; a peppy song that shoots stars at the Princesses and a sugary sweet song that makes men cheer for her. In the manga, she can make people (or at least a Mermaid Princess) dream about anything she wishes, including nightmares. In her real form she has green hair and pink eyes, in her human disguise form the eyes are brown and the hair color is the same (albeit retaining her pointy ears).