Phoenix: Endsong and Warsong
In 2005, the story arc "Phoenix: Endsong" began publication. During the course of this storyline, it was revealed that the Phoenix Force had once more survived the death of its host, and had gone on. Forced into a premature and incomplete rebirth by a rogue Shi'ar Empire crew and then attacked using an Eleka'an event horizon, the Phoenix was nearly destroyed. A remnant escaped and, harnessing the solar power of Cyclops' optic blasts, forced the dead Jean Grey back into life.
Immediately realizing that the Phoenix Force was not complete and thus a danger, Jean tried to prevent the Force from remembering what it had been looking for: Scott. As Jean spoke with Wolverine, she manifested the Dark Phoenix and blasted him. As Jean struggled for control, she forced a conflict with her former teammates, attempting to make them (specifically Wolverine) kill her before she was once more too powerful to stop. Seeking to prevent committing another act of genocide, Jean enlisted Wolverine's aid in weakening her in an arctic wasteland. Breaking open the ice with her telekinesis, Jean attempted to stop the Phoenix Force by encasing herself in the ice.
Abandoning Jean's body, the Phoenix Force manifested a semi-physical form and attempted to force Cyclops to use his powers - his optic blasts fed the Phoenix Force - only to be intercepted by Emma Frost, who offered herself as a new host. Emma quickly found herself being used up from the inside out, as her willpower wasn't strong enough to contain the overwhelming hunger of the Phoenix. Turning on her friends, Emma sought nothing but destruction and freedom.
Cyclops blasted the ice encasing Jean, and she burst forth. Once more, Jean sacrificed her own peace for the sake of her friends and the world. She ripped the Phoenix Force from Emma and proclaimed them the same being. Manifesting as Dark Phoenix, Jean struggled to control the cosmic force of the Phoenix, aided by the moral support of her friends, as Emma had her Stepford Cuckoos telepathically reach out to past and present X-Men and students at the Xavier Institute whose lives Jean had touched.
Manifesting the white and gold costume of the "White Phoenix of the Crown," Jean held back the event horizon of the Eleka'an by sheer force of will, saying a tearful goodbye to Scott once again, before Scott symbolically removed his visor for her, as he had done during the Dark Phoenix Saga. Jean then neutralized the event horizon and returned to the White Hot Room to restore herself and the Phoenix Force to full strength and to find their missing pieces.
At the end of Phoenix: Endsong, a piece of the Phoenix was seen approaching the Stepford Cuckoos. This storyline was continued in the mini-series Phoenix: Warsong. Greg Pak had this to say in an interview with Newsarama: "X-Men: Phoenix - Warsong is not a Jean Grey resurrection story. It's far too early to bring Jean back, both in terms of her own emotional storyline and the Marvel Universe as a whole. But we're doing our best to tell a story with Warsong that respects and deepens the Jean Grey/Phoenix mythos by exploring surprising new revelations and characters, pushing our heroes and themes to the next level, and laying the groundwork for the future." The story dealt mostly with the Stepford Cuckoos, John Sublime, Weapon XXII, and Emma Frost. In the end, the Cuckoos split the Phoenix Force and hold it within themselves.
Read more about this topic: The Dark Phoenix Saga