John Deegan

"My name is Dr. John Deegan, and I, like most of you, I'm a psychiatrist. Do you know what my patients tell me the most? They feel inferior. I'm here to tell you, whether we admit it or not, some people, they're just born lucky, which leads us to the real problem, imperfection. How can we ever hope to feel like supermen or superwomen without first becoming super ourselves?"

- John Deegan

Dr. John Deegan is a former psychiatrist from Gotham City, who was given the Book of Destiny to warp Earth-1 into Elseworlds. Changing reality multiple times, he has managed to give himself the destiny, looks and powers of Superman, copying Clark Kent of Earth-38. He was eventually defeated by Barry Allen, Oliver Queen, Kara Danvers and the real Superman, becoming engulfed in the energy from the Book of Destiny, which mutated John, disfiguring his appearance and psyche.

Early life
Deegan was born and raised in Gotham City. He graduated with a PhD and an MD in psychometrics, and became a psychiatrist at Arkham Asylum. His methods were bordering on torture conflated with illegal experimentation, however, he was never convicted and avoided prison over the years; due to technicalities. Despite this, Deegan did not completely get off scot-free; in 2013, his medical license was revoked and he was fired from the medical board.

Sometime before 2018, Deegan also started to work as a professor.

The mad scientist
One evening, Deegan was giving a presentation on his patients and how they could become meta-humans with the help of eugenic insights, but his audience then perceived him as insane and left before he even started elaborating, much to his disappointment and frustration. As he walked in the parking lot, he was approached by Mar Novu, who Deegan thought was a prankster trying to get some laughs, before Novu smashed his car in order to demonstrate his power and get his attention. When Deegan asked what the individual was, he remarked that he was something beyond his comprehension. The Monitor then gave Deegan the Book of Destiny, granting him the power to manipulate reality as he sees fit.

He tried to reshape reality with the intention to become the Flash, but miscalculated and caused Oliver Queen and Barry Allen to swap powers and identities.

Meeting the heroes
When Oliver showed up at Deegan's office in Arkham, he recognized and told him that he understood why he didn't become the Flash, stating that changing reality must have a "learning curve". As Oliver ordered him to fix reality, Deegan answered that he doesn't want to and runs away after releasing Arkham's inmates. When he retrieved the book from its hiding spot and was about to rewrite reality, Supergirl appeared and took the book from him, to which he quickly escaped.

Later, the Monitor appeared to Deegan once more in his lab holding the Book and asking him to think bigger. Deegan rewrote reality, on a larger scale.

A brave new Elseworld
After rewriting reality again, Deegan kept the book in the "Fortress of Solitude", jumbled everyone's lives, turned Oliver and Barry into criminals known as Trigger Twins, and took on the form of Superman, whose only record on Earth-1 was with his fight with A.M.A.Z.O.. He then pursued the Trigger Twins but was distracted when they caused an accident where he had no other choice but to protect the civilians and let them escape. Later at S.T.A.R. Labs, where he redesigned it as his headquarters, he ordered his agents John Diggle and Caitlin Snow to find them. He proceeded to the pipeline and conversed with "Subject One", Kara Danvers, who he locked up and drained off of her powers for himself, leaving Kara with a weaker version of her abilities. He revealed to her how he got the idea of his appearance and powers. Kara, in rage of Deegan's desecration of her family crest and her cousin, tried to break the glass, before Deegan's agent, Alex Danvers, administered a high-pitched sound to throw her off-balance, to which Deegan stated that the cells are patrolled 24/7. When agent Danvers left, Kara tried to call out to her, and much to Deegan's amusement, he threatened his own agent's life if Kara got any bright ideas of escaping, to which Kara called her a monster. Deegan said he was otherwise Superman. Later, he caught Alex Danvers breaking out Kara Danvers and was about to kill them when Barry, Oliver, Cisco and Clark breached inside S.T.A.R. Labs just in time for Clark to distract him. The two supermen battled within Central City, and civilians perceived them as Superman fighting one of his enemies, Bizarro. Deegan overpowered Clark and was about to finish him off, when Kara used her heat vision to throw Deegan into the air, and gave the Book of Destiny to Clark, restoring Barry's, Oliver's, and Kara's powers and abilities. Deegan saw this and threatened to snap Barry's neck if Clark didn't close the book. Oliver countered this by threatening to shoot a Kryptonite arrow, but let Barry talk him down to do otherwise. Deegan then saw an opening to create a thunderclap and escaped with the book. Deegan tried to restore his Elseworld in the middle of a crowded street, where police officers tried to stop him from causing mayhem, but were turned into helpless taxi drivers. He then summoned A.M.A.Z.O. from the Book of Destiny and kept Superman at bay, when J'onn J'onzz, Lois Lane, and Querl Dox breached in to assist, before A.M.A.Z.O. locked in battle with Brainy. Lois used the Solar Hammer from the Fortress of Solitude and kept Deegan off-balance, but not long enough for Clark to take hold of the book. Deegan retrieved the book and aimed it's energy at Clark and then at Lois, sending her flying. Barry and Kara successfully slowed down time, which gave Oliver the chance to shoot the book with a powerful arrow of metaphysical nature, overloading it with energy and destroying it's powers, and reverting reality back to it's original state. The accumulation of energy also disfigured Deegan's face and cognitive abilities.

Inmate at Arkham
John was then locked up at Arkham Asylum, this time as a patient, where he became friends with Roger Hayden, who told him not to worry as, due to his to actions, "the stage was set" and soon "worlds will live, worlds will die, and the universe will never be the same".

Personality
"Idiots!"

- John Deegan

John is passionate about his work as a psychiatrist, too passionate that fellow psychiatrists call him Frankenstein and a mad scientist. He even went far as to experiment on deranged patients in Arkham Asylum. But this was possibly because he only thought that this was a better way to help patients.

John was proven to be not only be knowledgeable in his field of psychometrics, but to also be a creative thinker and a visionary. This was evident when Mar Novu picked him as the user of the Book of Destiny and when he created his second Elseworld, as creative minds can create diverse outcomes.

John was proven to be extremely selfish, as he wanted powers like the Flash's and Superman's for himself and did whatever it took to achieve it, this was also seen when he fought Clark and threw a manned helicopter to distract him, and when he caused mayhem in a crowded street, not considering the lives at stake. While perceiving himself as a "hero", even in the new world he had created for himself others recognised that they were mainly there to prop up his own ego, to say nothing of his attempts to become a hero focusing on taking the power and identity of others rather than adopting his own identity in the first place.

Former powers

 * Abilities via the Book of Destiny: Using the book, John was able to perform mataphysical feats, until the book's powers were destroyed.
 * Metaphysical connection: The lock of the Book of Destiny only shared a metaphysical connection with Deegan, letting him unlock the book.
 * Essokinesis/Reality manipulation/Elseworld creation: Once opened, the book allowed Deegan to manipulate reality to how he saw fit in the blink of an eye.
 * Kryptonian physiology: While becoming Superman through Book of Destiny, John's capabilities are no greater than a normal human of his physical conditioning. However, once charged by the energy spectrum of a yellow sun, he becomes able to perform various inhuman feats.
 * Solar energy absorption: While John's powers are dependent on the energy spectrum from a yellow sun, the stored up energy allows him to use his powers without constant exposure to the solar radiation until finally depleted.
 * Accelerated healing factor: John's solar charged metabolism accelerated his rate of healing.
 * Flight: John is able to manipulate his own gravitational field to generate thrust and propel himself through the air at tremendous hyper-sonic speeds, much faster than he can travel by foot.
 * Heat vision: By concentrating every solar energy reserve he has in his body, John can emit blue energy beams of variable intensity from his eyes.
 * Invulnerability: With his cells supercharged with solar energy, John's bodily durability is considerably stronger than even the densest of Earth's metals such as steel.
 * Super speed: As a Kryptonian, John was able to move and react at high speeds.
 * Super strength: As a Kryptonian, John was far stronger than a normal human, as well as some aliens. However, despite this, John was not as strong as the real Superman, as the book only replicate the powers of the kryptonian, they did not put him on the same level as Superman; the only reason why he managed to overpower the latter was due to the fact that Clark was considering the lives at stake, well John had no concern for innocent lives at all.
 * Absolute reality perception: Once opened, the book enabled John to look at the whole of reality.
 * Ergokinesis: The book allowed John to release surges of energy powerful enough to even harm Kryptonians.

Former abilities

 * High-level intellect/Expert teacher: John is an accomplished scientist, a psychiatrist and a researcher, although his methods border on torture and conflate with illegal experimentation. Aside from his job at Arkham Asylum, John also works as a professor.
 * Escape artist: John was able to plan his escape from Arkham Asylum in case the superheroes realized that he was behind the changes to the timeline, successfully escaping from Green Arrow and the Flash with the use of prepared traps and distractions, and later managing to improvise and slip away from under Supergirl's watch.
 * Peak of human reflexes: John possesses incredible reflexes for a human of his age and build, "slippery" enough to escape the Flash, Green Arrow and Supergirl.
 * Peak of human speed: John possesses high speed for a human of his age and build, "slippery" enough to escape the Flash, Green Arrow and Supergirl.

Former weaknesses

 * Kryptonite: Having a Kryptonian physiology, kryptonite can prove fatal to John when in close proximity or pierced under the skin.

Former equipment

 * Book of Destiny: Mar Novu bestowed unto Deegan a book which allows him to alter reality, until it was destroyed by Oliver Queen.
 * Superman suit: While he posed as Superman of Earth-1, he wore a protective black suit.

Behind the scenes

 * In the main DC Comics continuity, John Dee, also known as Doctor Destiny, is a supervillain with the power to bring dreams to reality. He is an adversary of the Justice League of America and is prominent in Neil Gaiman's The Sandman series, in which he sports a disfigured face similar to that of his current form in the Arrowverse,.
 * Doctor Destiny is associated with Dreamstone, artifact created by Dream of the Endless, while his Arrowverse counterpart uses Book of Destiny, artifact created by Dream's older sibling Destiny of the Endless.
 * Deegan's actor, Jeremy Davies, previously appeared in ​​​​​ as Ritchie Simpson.
 * In the Episode 'A Whole World Out There', Ritchie and John adventure to a new reality, with Ritchie eventually modifying it to his own vision: similar to how Deegan modified reality in Elseworlds.
 * In the movie Justice League Dark, which also featured Jeremy Davies as Ritchie Simpson (and Matt Ryan as Constantine), the antagonist John Dee/Dr. Destiny manipulated Ritchie throughout the movie and ultimately took over his body.
 * Deegan's appearance and attitude as the Black Superman is similar to superhero-turned-villain Superboy-Prime, specifically during the Countdown to Final Crisis limited series.