Phoenix

While Emma Frost was lay in a comatose state, Dr. John Sublime harvested eggs from her to begin experimentation. The Weapon Plus program began the cloning to develop a powerful weapon capable of killing every mutant on Earth by combining their telepathic abilities. The project was designated Weapon XIV, and girls were incubated and artificially aged inside the subterranean level of The World. Thousands of girls were cloned from the ovum, but while the others remained dormant, five girls were sent to infiltrate the Xavier Institute as student sisters to hone their talents for Sublime's purpose.

After the Xavier Institute went public, Celeste and her sisters were enrolled as orphan quintuplet sisters. To protect their secret origins, the girls unconsciously placed mental blocks in the minds of the faculty, preventing them from investigating their background. The girls quickly gained the moniker "The Stepford Cuckoos", though their chosen codename was the Five-In-One. Emma Frost took a special interest in the girls, and the Cuckoos became her protégés. When Kid Omega led a rebellion of students at the X-Mansion, Sophie encouraged Celeste and the other Cuckoos to take action, and they covertly snuck into Cerebra. Using Kick to amp up her powers, Sophie and her sisters were able to stop Quire. Unfortunately, Sophie died in the process. With the death of Sophie, the Five-In-One became the Four-In-One. The girls were furious with Emma Frost, whom they blamed for Sophie's death. This mourning and anger was multiplied when Esme attempted to murder Emma, fled the X-Mansion, and joined Xorn's Brotherhood. With the departure of Esme, the Four-In-One became the Three-In-One. When the Institute was rebuilt under the leadership of co-headmasters Cyclops and Emma Frost, the students were organized into several training squads with an assigned mentor staff member. Celeste and her sisters were assigned to the Corsairs Squad under the tutelage of Cyclops with the girls serving equally as co-leaders of the squad.

On M-Day the vast majority of the world's mutant population was depowered. Celeste and her sisters retained their powers, but they were three of only twenty-seven students to retain their powers. Fearing for the students' safety, Emma Frost ordered that the depowered students and staff leave the Institute. For their safety, the depowered students were brought through the Morlock Tunnels to an awaiting bus. Unfortunately, the bus of depowered students was bombed by anti-mutant zealot Rev. William Stryker, killing all forty-two of the former students on board. The remaining students were placed by Emma Frost into an all-out brawl, and the ones deemed the best by Emma would become a group of New X-Men in-training. This entire exercise was met with disgust by the Three-In-One, who promptly informed Cyclops of Emma's actions.