BIOGRAPHY - PAGE 3
The Cuckoos were some of the many students kidnapped by the demon Belasco and taken to his realm of Limbo. Knowing that they were a great threat to him, he locked their heads in helmets, inhibiting their telepathy. The rest of the students eventually fought back against him and freed the girls, who set about seeking revenge. Though they forced their way into his mind and discovered why he was attacking the teens, he ended up being too strong and pushed them out. Belasco was eventually defeated by the X-Men and the girls returned back home to the Institute. [New X-Men (2nd series) #38-41]
Despite everything that had been going on, the Cuckoos still remembered that Prodigy had saved their life when Stryker attacked the school and they decided it was time to repay him. He had been one of the many students depowered on M-Day, losing his computer-like mind in the process. The Cuckoos explained that, even though he wouldn’t be able to learn anything new at an accelerated rate, they could at least unlock all the knowledge he had previously acquired. Prodigy was wary but he reluctantly accepted the deal and the girls restored his superior intelligence. [New X-Men (2nd series) #43]
Ordinarily, students weren’t allowed to use Cerebro, because it was considered too powerful and dangerous for their psyches, but the combined might of the Cuckoos’s hive mind meant they could take the strain. They soon started to be relied upon more when the senior X-Men were away and their skills came in handy when the first new mutant signature was discovered after M-day in the form of a newborn. The X-Men were busy trying to track the baby down and it was the Cuckoos who eventually found it in Cable’s care. The girls became key in coordinating the various X-teams across the world in stopping the threats to the child. [Messiah Complex crossover]
During the events in tracking down the baby, the Institute was destroyed and Professor X was seemingly killed. The X-Men relocated to San Francisco to start anew and the Cuckoos followed them there. The girls’ skills were immediately required when the Skulls attacked Earth and the X-Men set about defending the city. As well as helping coordinate the various X-Men around San Francisco, the Cuckoos were also needed to help Emma Frost break through the aliens’ 
formidable psychic defenses. When Emma fell into a trap and her body stopped functioning, the Cuckoos used their psychic abilities to force her brain to keep her motor functions going until her mind came back to her body. [Secret Invasion: X-Men #1-4]
The Cuckoos aloof nature meant that they were often trusted with important information of which only the senior X-Men were aware. They were some of the very few people to learn about the existence of Cyclops’ wet-works squad of X-Force and often aided the team in their secretive missions. [X-Force (3rd series) #7, 12-13, 19-20]
With the threats to the mutant race becoming increasingly common and severe, the Cuckoos found themselves being utilized more and more as the team’s go-to telepaths. Whether it was Madelyne Pryor’s Sisterhood, Norman Osborn’s Dark Avengers or Selene’s army of the undead, the girls proved themselves not only as effective psychics but also skilled fighters as well. [Uncanny X-Men (1st series) #508-511, Utopia crossover, Necrosha crossover]
During another of the numerous attacks to the X-Men’s new island base of Utopia, the Cuckoos were providing their usual coordination support when they were caught off-guard by the Phoenix Force. In the middle of a battle between the X-Men and the deadly Predator X creatures, the girls doubled over, as the Phoenix erupted out of them and flew off into space. The Cuckoos were knocked unconscious by the event and the X-Men were momentarily disorientated by the loss of the psychics during the fight. [Uncanny X-Men (1st series) #516-518]
[Note: Whilst it wasn’t stated at the time, the fragments of the Phoenix Force were most likely gathering themselves together for the Phoenix’s arrival during the Avengers vs X-Men event a few years later. Rachel Grey and Korvus Rook’shir also lost their portions of the Phoenix Force around the same time.]
The Cuckoos became the target of Quentin Quire’s wrath when his mind escaped its containment 
unit and he set out to destroy the X-Men. He trapped the three girls in a mental loop, ensuring they would remain clueless until the moment he killed them. However, he didn’t count on No-Girl, another psychic on the island, being cleverer than him and setting the Cuckoos free. Angered by the attack from Quire, they showed him how powerful they had truly become by defeating him once more and sending his mind back to the vat of protoplasmic energy it had come from. [Nation X #2]
Cyclops became concerned about the Phoenix leaving the Cuckoos, so he had them use Cerebro in a bid to locate it deep in space. Knowing that the cosmic entity would actively hide from a direct psychic scan, the Cuckoos decided to lower their power level in a bid to scan for it passively. They used Rogue to syphon off enough of their power so they could look, but their efforts were for nothing as they could not find a single trace of the Phoenix. [X-Men Legacy (1st series) #234]
The loss of the Phoenix Force was starting to take its toll on the Cuckoos, as they were now slightly weaker than before and they were able to feel things again. In fact, they mostly felt boredom of the monotony of island life and started to take their frustrations out on those around them. Becoming inspired by horror movies, they started to trap their unsuspecting teammates in vivid illusions of scenes taken directly out of them. Emma Frost caught onto their schemes though and confronted them about it. As punishment, she made them do some of the more menial tasks around the island, but she also gave them the chance to become teachers to the younger students. Despite complaining about it, the girls began to thrive in their new role. [Nation X #4]
When the ancient Chaos King unleashed his attack on the world, he managed to put all the 
superheroes of Earth to sleep and destroy the Underworld, allowing the dead to rise once more. Afraid of what was going to happen, the Thunderbird, a Native American god, resurrected a number of mutants, including Esme and Sophie. The two girls immediately came to blows as Sophie was angry at being killed by Esme, but her sister refused to apologize for her actions. The confused group split up to discover why they were alive, giving the two girls a brief moment to reflect on their deaths.
They soon discovered clues that pointed them in the direction of Muir Island, but they attracted the attention of the Carrior Crow, a Native American god who ate souls. John Proudstar, another of the resurrected, summoned his Thunderbird god and opened a portal to Muir Island. The Carrion Crow attacked them before they could all get through and Sophie sacrificed herself to save the group. Unfortunately, Sophie was not killed but rather corrupted into a raven-like creature to serve alongside the Carrion Crow. Using the sister’s telepathic link, they followed the mutants to Muir Island, where Sophie’s corruption started to spread to Esme. The young girl tried to resist and, as the Crow attacked the rest of the group, the 
two sisters went head to head. Sophie managed to regain her senses long enough to tell Esme that killing her would weaken the Crow significantly. Sophie gave her sister the opportunity to kill her once again, but Esme refused to do it, declaring that she loved her sister.
As John used a spell to tap into the elemental spirit of the Earth, a power he hoped would destroy the Crow, the ancient villain revealed he had tricked the group all along. Through the Cuckoos telepathic link, he was able to use the elemental spirit for himself and rule over the Earth. Esme was furious and attacked the Carrion Crow but was instantly killed by him, much to the devastation of her sister. Ultimately, John managed to defeat the Crow and deal a crippling blow to the Chaos King’s plans. After the fight, Sophie and John bonded over the recent events, with Sophie proclaiming she was proud of Esme and had forgiven her. Sophie too returned to the grave once the Chaos King was defeated, with the rest of her sisters never realizing the heroism that she and Esme displayed. [Chaos War: X-Men #1-2]