After staying at the Jean Grey Institute, the Stepford Cuckoos left and joined Cyclops' school and his team of mutant revolutionaries.
Major Story Arcs
During the events of Riot at Xavier's, Sophie convinces Mindee and the others to take Kick and use Cerebra to stop Quentin. Sophie leads by entering the machine and taking Kick while the others help her. after they destroy Quentin, Emma reveals that Sophie had died in the machine.
The four living sisters get revenge against Emma who they blame for Sophie's death, by alerting Jean to Scotts affair. Esme later shoots Emma in the imperfection in her diamond form and shatters. When it is revealed that Esme is the attempted murderer, it is to late and the institute is destroyed and she is with Xorneto. This back fired when Esme is killed by Xorneto leaving the Cuckoos the Three-in-One.
Celeste is more the teacher’s pet than any of the others. We only start to see emotions in Phoenix: Warsong. In Phoenix: Warsong, Celeste didn’t think it was time for them to demonstrate their power at first. When they went flying she didn’t feel like they should. She is the one who told Emma that it wasn’t her fault. She goes to Beast to see what’s happening to her and her sisters.
The girls later decided to help both Elixir and David. They gave Elixir all the medical knowledge of Beast and gave back everything David had ever had learned using his powers. When Belasco came to the school looking for Magik, the three were put into special helmets to prevent the use of their telepathy. When the helmets were removed the three were crucial in the defeat of Belasco.
The girls helped find Hope, before Cerebra was destroyed.
The girls helped with coordinating during Secret invasion, but when the thought wall was implemented, they were all but useless. Emma died when she tried to break the wall, and the girls were given the job of keeping her alive until she returned.
Quentin once again came back and was going to destroy the X-Men, but was stopped when the Cuckoos were alerted to his presence by Martha. They told him that they had become much more powerful now that their was only the three of them and the easily beat the omega mutant. Irma was used to infiltrate the mutant prison that Norman created to combat the mutant presence in San Fransisco. she was captured which allowed the X-Men to infiltrate the base and save Xavier and Beast among others. During the Predator-x battle on the island, they linked every X-men with their telepathy but the girls lost the Pheonix force that inhabited their hearts leaving them unconscious.
Powers and Abilities
Celeste is a powerful telepath. She and her sisters have been able to merge their telepathy and have their powers resonate, creating a psychic mind stronger than almost any other telepath and they were even able to defeat Kid Omega, an Omega level mutant.
After it is revealed that the Cuckoos are actually the genetic offspring of Emma Frost, the Three-In-One all manifest the ability to turn into diamond. However their diamond form is perfect, without a fault. They also had the power of selecting what part was turned to diamond, i.e. able to turn their hearts diamond only.
Briefly the Three-In-One were the Phoenix host. This happened after Jean died again in end song. Unable to control the full abilities of the Phoenix force, they split it into three and each housed a portion in their now diamond hearts but they lost it during the Predator-x battle.