Phoenix was physically an exact duplicate of Jean Grey with some of her "essence" or memories intact, created by the Phoenix Force. When this being became uncontrollably hostile and violent, the green parts of her costume would turn red.
This cosmic manifestation first came into being underwater after a space shuttle crash. While the real Jean Grey was being cocooned, this entity rose from the water. The Phoenix entity became too strong to control, for the merely human aspects it had acquired from Jean, but the other X-Men had no way to know what was happening and little chance of preventing a tragedy. Professor X helped Jean establish "psychic circuit breakers" in her mind, but they became less and less effective.
She was thus an easy target for the illusionist Mastermind, who needed a trophy to join the Inner Circle of the prestigious (and infamous) Hellfire Club. With the help of a psionic device created by the club's White Queen, Emma Frost, Mastermind made Jean believe that she was his 18th-century lover, Lady Grey. Jean joined the club as their Black Queen, which would allow her to relish the extremes of human emotion and sensuality. When the X-Men came to her rescue, Jean's true love, Cyclops, faced Mastermind in a psychic duel and was defeated. His "death" broke Mastermind's hold over Jean's psyche--as well as any control that Jean had over the Phoenix. It brushed aside the X-Men and departed for the heavens.
To sate its hunger, the (now Dark) Phoenix flew to a distant galaxy and devoured the star of the D'Bari system. The resulting supernova killed billions of innocent people. A Shi'ar vessel attacked it and managed to alert the Shi'ar Empress Lilandra before they were destroyed. The empress called a council of her intergalactic counterparts, including the Kree and Skrull empires. They concluded that, for the rest of the universe to live, Dark Phoenix must die.
Meanwhile, the Beast had found a way to neutralize Phoenix's power temporarily. When it returned to Earth, the X-Men held it at bay while Professor X rebuilt the circuit breakers in Jean's mind. At that moment the Shi'ar arrived and teleported everyone aboard their flagship. Lilandra announced that Phoenix, and thus Jean Grey-Summers, would have to die. Jean received a Kree weapon so that she could "do the right thing." Professor X, unwilling to give up on one of his pupils, but romantically involved with Lilandra, challenged her to Arin'n Haelar, a Shi'ar duel of honor that cannot be refused. Professor X named the X-Men as his champions in the duel, Lilandra her Imperial Guard.
The duel took place the next day in the Blue Area of the Moon. The Imperial Guard made short work of the X-Men, leaving Cyclops and Phoenix to make a final stand. A stray bolt hit Cyclops. Jean's control broke, and she became the Dark Phoenix again. Lilandra ordered Plan Omega, which would destroy the whole solar system in hopes of eliminating Dark Phoenix as well. Professor X ordered the X-Men to subdue Jean so that Plan Omega would not be necessary, and they managed to subdue the Phoenix for a brief time. In this moment of lucidity, Jean took Cyclops to a back alley, where she bade him an emotional farewell and turned the Kree weapon on herself.
The story ends with Uatu the Watcher's comment: "Jean Grey could have lived to become a god, but it was more important to her that she died as a human."
Powers and Abilities
Known Powers: Like Jean Grey-Summers, the Dark Phoenix used telepathy and telekinesis, but at a much higher level. She was able to rearrange the molecular structure of matter and fly at supersonic speeds. Using the Phoenix Force, she could travel through hyperspace and destroy Shi'ar battlecruisers with little effort.
Known Abilities: Because Phoenix was linked to Jean's psyche, she maintained a psychic link with Cyclops.
Strength Level: As Jean Grey-Summers, the Phoenix possessed the normal human strength of a woman of her age, height, and build who engaged in moderate regular exercise. Using her cosmic powers and telekinesis, Phoenix could lift an unknown amount, probably in the range of thousands of tons.
Appearances in other media
In the movie X-Men: The Last Stand, it is revealed that Jean is a "Class 5" mutant, arguably making her the most powerful mutant in existence. In this film, Jean appears as the Phoenix/Dark Phoenix. When using her Phoenix powers, Jean's appearance changes considerably: her skin becomes pale, dark and veiny, her eyes turn black (although fire can be seen in her irises at certain points in the film), and the color of her hair changes from its natural dark red to a bright, almost fire-like, reddish-orange. As a child, Xavier put psychic blocks around Jean's subconscious mind to keep her immense powers at bay. As a result, Jean developed a split personality called "The Phoenix." Dark Phoenix emerges from the lake where Jean had died and apparently kills Scott Summers. During a confrontation with Professor X at Jean's childhood home, Dark Phoenix lashes out and lifts Xavier out of his wheelchair with her telekinesis and horrifically atomizes him, destroying the house in the process (caused when her outburst of power causes everything in the house that's not nailed to the floor to crash up onto the ceiling, and then causes the entire house to float up in midair).
After she kills Xavier, she leaves the ruins of her old home with Magneto and joins, albeit unofficially, the Brotherhood of Mutants. During the attack on Worthington Labs, Dark Phoenix resurfaces when a group of soldiers fire cure darts at Jean. Dark Phoenix freezes them in place and disintegrates them along with the soldiers. She then goes on a rampage and destroys much of Alcatraz Island, killing mutants and humans alike. Wolverine gets Jean to resurface by professing his love for her. Since she can't control Dark Phoenix for long, Jean pleads with him to kill her rather than let her harm more people. He fatally stabs her with his claws, and as the freakish features of Dark Phoenix dissipate, Jean becomes herself once again before dying. The ending scenes show her grave marker alongside Cyclops and Xavier's on the Institute's grounds.
Follow link for an overview of the film Dark Phoenix (2019): https://youtu.be/AdciYf3Xwxk
X-Men Animated Series
Dark Phoenix - X-Men Animated Series. Dark Phoenix appears in X-Men Animated Series in The Dark Phoenix Saga (episodes 37-40).
The Dark Phoenix Saga Part 1: Dazzled The Phoenix continues to inhabit Jean's body, brazenly taking over at will. As a chanteuse named Dazzler flirts with Scott, Jean/Phoenix finds herself psychically seduced by Mastermind (Jason Wyngarde), with help from Emma Frost and the other mutants in the Inner Circle Club. Wyngarde weaves a new history for the confused Jean/Phoenix, creating a passionate romance between himself and her. When the X-Men come to rescue Jean, they find her fighting alongside Wyngarde -- her fiance.
The Dark Phoenix Saga Part 2: The Inner Circle As Professor X and Emma Frost battle for psychic control of Jean, the Inner Circle members quarrel over how to dispose of their prisoners the X-Men. Is Jean and Scott's psychic connection gone forever? Or is she strong enough to overcome Phoenix's influence and Wyngarde's trickery to remember who she is...or at least was?
The Dark Phoenix Saga Part 3: The Dark Phoenix When the X-Men confront Phoenix to give up Jean's body, Phoenix vows to destroy the team. To re-energize, she flies up through the D'Bari Star System, passing a very surprised Shi'ar Star Cruiser crew. As they watch in horror, she feeds upon and destroys an entire star system. To defend space life as they know it, the Shi'ar empress Lilandra decrees Phoenix/Jean Gray must die.
The Dark Phoenix Saga Part 4: The Fate Of The Phoenix The X-Men battle Lilandra's Imperial Guard for 'custody' of Phoenix/Jean Gray. Although Xavier and Lilandra wish they could settle amicably, they are set on opposite courses. When Phoenix falls in battle, Xavier startles everyone by commanding the X-Men to stop Phoenix now, while she is vulnerable. But how can Cyclops, Wolverine, Storm or any of the team strike Phoenix while she inhabits the body of their dearest friend and teammate Jean Grey-Summers? And what will happen if they don't?
The animated TV series X-Men: Evolution end with glimpses of the future for various characters, and Jean Grey is shown transforming into Dark Phoenix .
Wolverine and the X-Men
During this animated series, we can see five Dark Phoenixes, who are from the Hellfire Club.
Dark Phoenix - X-Men Legends II: Rise of Apocalypse Dark Phoenix appears in X-Men: Next Dimension for the PS2, Xbox, and Nintendo Gamecube. Dark Phoenix is also a playable character in X-Men Legends and its sequel X-Men Legends II: Rise of Apocalypse (exclusively for PSP version of the game). In Marvel Vs Capcom 3, Jean turn into Dark Phoenix when she dies with a 5 level hypercombo bar. Dark Phoenix also appears in the PlayDom flash game Marvel : Avengers Alliance, as a boss during a special limited mission inspired by Avengers Vs X-Men comics. She also appears as a playable character in Lego: Marvel Superheroes but has no mission storyline.
The Dark Phoenix story raised the standards for graphic storytelling. Claremont's use of foreshadowing, motivation, and pathos took comics to a new level and made the X-Men franchise one of the most popular titles ever. Uncanny X-Men 101-132 Uncanny X-Men 132-134 Phoenix (Phoenix Force) took the name "Jean Grey-Summers" in Uncanny X-Men 101 and maintained that impersonation throughout the Dark Phoenix Saga, although neither Phoenix nor Dark Phoenix was actually Jean.