What is Phoenix Force?
The Phoenix Force is one of the most powerful beings in the Marvel Universe, possessing the unlimited power to create and destroy anything and everything. It has been stated to be an Extinction-Level Threat by Quicksilver and an Omega-Level Threat by Mister Fantastic.
While how the Phoenix Force works is not clear, it seems to amplify existing emotions. As the emotions grow, the host's perspective grows infinite. Individual feelings like joy, grief, and love for another become insignificant. The memory of even incredibly traumatic events, such as Scott Summers's memory of Jean Grey's suicide on the moon, fades.
The Phoenix Force's powers include:
Nigh Omnipotence: The Phoenix Force is practically omnipotent, however it is limited in undetermined and undefined ways as seems to suit its current mission/purpose. As the White Phoenix of the Crown, it was able to warp reality on a universal scale. This was not the result of divergence, but rather the effect of reality manipulation which changed history.
Future Life-Force Tap: The Phoenix Force can tap into the energy provided by life-force reserved for future generations, thus denying them existence. The Phoenix Force possesses limitless cosmic energy. With or without a host, it is one of the most powerful entities in the Marvel Universe, capable of existing in any plane, time-line or dimensional existence.
Concussive Force Blasts: It can wield this energy to project beams of immense concussive force powerful enough to destroy whole planetary bodies.
Quantum Singularity: It can transmigrate throughout time and space by folding its energy back into itself, causing it to collapse akin to a black hole. It then reforms itself upon reaching its destination, much like the Phoenix of ancient myths.
Energy Absorption: It can directly absorb, manipulate, and fully control any type of energy such as Cyclops' ruby-red-colored optic blasts or the entire energy of a star, black hole, or even a whole galaxy. Jean, as the "One-True Phoenix", was shown to be able to activate and deactivate the mutations of other's with just the use of her psychic abilities.
Life-Force Control: The Phoenix Force can control and manipulate life and death itself, as such, it can take the "life energy" from something, rendering it "dead" or vice versa.
Psionic Nexus: As the nexus or center of all psionic energy throughout the cosmos, the host attains nigh-infinitely powerful mental abilities, including telepathy, empathy, and telekinesis, and often seeks out hosts who have psionic abilities (i.e. Nate Grey, Jean Grey-Summers, The White Queen, and The Cuckoos). When bonded with a host, the Phoenix Force vastly strengthens and amplifies all of their superhuman mutant powers and abilities to immeasurable and innumerable power levels that have been shown to be near unlimited such as the Phoenix's one-true host.
Matter Transmutation: It can manipulate and transmute matter on a subatomic level (e.g., turning wood to gold, stone to crystal, cause physical bodies to disintegrate, convert Homo mermanus to Homo superior, etc).
Cosmic Teleportation: It can teleport others across vast distances such as another planet or galaxy, and the vast vacuum of space itself or even an entire timeline all-together.
Disintegration Waves: It can consume and remove a near infinite amount of molecules per second.
Resurrection Force: It can resurrect anyone it wishes with its near infinite powers, as it is the embodiment of life and death itself. It could also bring itself back as well as its host (it has done this many times over in the form of Jean).
Immortality: The Phoenix Force is immortal and indestructible. It cannot die or be destroyed. After its "death" in Avengers vs. X-Men it was said to be destroyed, but, as it has happened many times, the entity never truly died. It forms itself in a cosmic egg in the White Hot Room and stays in there until it is ready to come out. Some hosts get true immortality, but other get it from never aging or needing food, water, and oxygen to breath and, if they were killed, the Phoenix Force would bring him or her back to life.
Cosmic Pyrokinesis: It can create 'cosmic' flames under any conditions even the impossible ones such as vacuum space or underwater. These flames do not require oxygen to burn, and burn so intensely that matter is consumed without by-products such as ash. It has perfect control over these flames, and they only consume what it wills. These flames are shown to be able to burn even underwater. Typically they manifest as a raptor or part of a raptor such as a claw or wings, in the case of an avatar. It is unclear whether these flames are an extension of its powerful psionic abilities or a literal punctuation to its purpose to 'burn away what doesn't work.'
Temporal Manipulation: The Phoenix Force can manipulate the past, present, and future across large temporal distances and with a profound knowledge of the causal effect her actions will have. It may be the case that time as a concept doesn't apply to the White Hot Room. it has only been shown when Jean Grey as the White Phoenix of The Crown held her universe in the palm of her hands, possessing the infinite power to write what she would as the "One True Phoenix" in any timeline, using to save her timeline from becoming a horrible future, altering the memories of everyone in reality itself in the process.
Atmokinesis: The Phoenix Force is capable of manipulating and creating cosmic weather. It can create cosmic storms, solar flares, geomagnetic storms, cosmic rays, coronal mass ejection and black holes.
Existence Mastery: It possesses total control over the entire existence as shown by The White Phoenix of the Crown (c.f. The White Hot Room). It can warp the reality, bring anything into existence, freely manipulate all existing things, and return them to nothingness when their purpose is extinguished.
Its immeasurable cosmic powers and abilities appear to be at their strongest and most powerful when bonded to Jean Grey ("the One-True Phoenix" who is completely compatible with the entity, possessing incredibly strong and powerful levels of telepathic, empathic, and telekinetic godhood status abilities, complete control and manipulation over the realms of matter, energy, space, time, existence and thought), as the two have a strange, profound connection to each other (Jean is the closest thing the Force has to physical form). It has yet to explain how Jean is "the true phoenix" and why.
Like Jean Grey-Summers, the Phoenix used telepathy and telekinesis, but at a much, much greater near-limitless power levels (unlimited as White Phoenix). She was able to rearrange the molecular structure of matter and fly at high hypersonic speeds while inside a planetary body. Using the Phoenix Force, she could travel through hyperspace and destroy Shi'ar battle cruisers with little effort.