Deus Ex Machina

Deus Ex Machina is the God of Time and Space and a major character in both the Future Diary manga and anime. Co-creator of the Future Diaries alongside John Bacchus, Deus creates the Survival Game to find a suitable successor to his title before his imminent death causes the destruction of the universe. Able to manipulate time, space, and the laws of cause and effect, Deus is the most powerful entity in the series, acting as the judge of the Survival Game.

Appearance
Deus is an extremely large figure, towering over other characters at well over a hundred feet tall. Barely humanoid in appearance, Deus has a head resembling the skull of an unknown creature, a shock of white and purple hair, a golden crown, and long pale arms with claw-like fingernails. The rest of his body is hidden beneath a dark cloak with a high collar and golden adornments, with a red and purple band around the neck area.

Personality
Despite being a god, Deus is very playful and laid-back, seeking courses of action that will amuse him in addition to achieving his goals. Unfortunately, he is completely apathetic and/or oblivious to the consequences of his "games". In his first appearance alone, he is shown provoking a war for fun, and he develops the Survival Game without thought to the consequences for the participants being forced to kill each other. He also seems to have chosen several participants based on how "interesting" they will make the game, regardless of their motives to become his successor. As a result, many of the Survival Game candidates are planning to use their eventual godhood for selfish and destructive ends - with some plotting to destroy the universe outright - and others have no desire to play the game at all. Furthermore, while Deus never outright lies, he is not above manipulating the truth to achieve his desired goals, such as evading Yuki's question over whether or not he could revive the dead as a god.

Although far from a benevolent god, Deus is not without compassion and has on few occasions done good things without any personal profit. Prior to the Survival Game, he saved Minene Uryu from death despite her hatred of gods, offering her a Future Diary and a place in his game without coercion. Additionally, while Deus's rationale for holding games is often incomprehensible, he shows a clear sense of honor when the Survival Game is in progress, answering the participants' questions and doing whatever he believes necessary for the game to be as fair as possible. He appointed/created a special observer to collect information on the participants and report any serious deviations from the game, and sent Minene on a mission to stop Muru Muru from unfairly supporting Yuno. In the latter case, he even gave half of his own knowledge and powers to Minene in order to aid her mission, despite accelerating his own demise in the process.

Deus appears to have extended relationships with the different diary owners. The fact that he interacts with certain humans (seemingly without any explanation) implies that Deus may, in fact, be fond of some humans, or at the very least those whom he finds to be interesting.
 * He is rather fond of Yukiteru, at first posing as his imaginary friend and personally makes him the "First" diary owner. Deus openly supports Yukiteru throughout the game, unphased by Yukiteru's mishaps and believing it is all part of his future to become his successor.
 * He also has a unique relationship with Minene Uryu, who does not believe in God and wants nothing more than to rid the world of the very concept of a deity (which would include herself if she won the Survival Game). After being made aware of Deus's existence, Minene openly hates him but is willing to ask him for advice, and even protests to receiving a portion of his powers when the time comes. For his part, Deus views Minene as an ally and admires her ceaseless determination in the face of adversity, choosing her for his plan to counter Muru Muru's scheming.
 * Deus and John Bacchus seem to be good friends, creating the Future Diaries together. John seems to care for Deus, but also uses Deus' needs as an excuse to extend his own plans in the Survival Game, requesting that Yukiteru and Yuno be eliminated from the game to speed it up before Deus dies.

Powers and Abilities
Deus is an ancient deity who rules over time, space and the laws of causality. It is implied that he may be able to rewind time, but leaping back in time can create parallel worlds. He has control of the Akashic Records, the universal compendium of knowledge and history. He is shown to be able to create artificial lifeforms, namely Aru Akise, revealed to be his "Observer" in the survival game to keep track of the ever-changing futures of the diary owners.

Deus operates from the Cathedral of Causality, depicted as a large domed building with purple lighting. Deus sits in a large throne which hovers just above the ground amid a partial sphere of metal fragments; he can also summon a "resting sphere" around himself to conserve energy and have private conversations with others. The cathedral also has an arena where Deus and Muru Muru summon the diary holders for occasional meetings. The arena is covered with an endless cloudy sky, revealed to actually be a cover for the Akashic Records. As Deus's death draws nearer, his body, throne, and the Cathedral itself all begin to crumble and fall apart.

Despite his tremendous power, even Deus has limitations. He remains oblivious to the existence of the first alternate world, implying he only has power over the time and space of the universe he lives in. He also cannot resurrect the deceased, only restore their physical bodies as soulless shells.

While Deus's true lifespan is unclear, it is both finite and inextricably tied to the universe; without a God of Time and Space, all of creation will be destroyed. The Survival Game is an elaborate means for Deus to find a successor to continue maintaining the universe following his death.

The First World
Not much is known of Deus during the first iteration of reality, but he eventually reached the end of his lifespan and began seeking a successor to his title. With the help of John Bacchus, Deus developed the Survival Game in order to find a worthy heir; the exact details are unknown, but Deus apparently oversaw the game from beginning to end without any apparent need to act. It is suggested he died at 28th of July, shortly before Yuno Gasai won the game.

The Second World
In the series proper, Deus is introduced as Yuki's imaginary friend. He empowers Yuki's phone to become a Future Diary roughly 90 days before his predicted demise; when Yuno reveals that she also possesses a Future Diary, Deus notes that he never said that Yuki was the only one to receive the gift. Following Yuki and Yuno's victory over Takao Hayama, Deus summons the remaining participants to the Cathedral of Causality to formally introduce them to the Survival Game. After explaining its purpose, the rules, and some basic information about the Future Diaries, he specifically names The First (Yuki) as his favored candidate to succeed him.

Deus continued observing the game from his Cathedral with little comment until Yuki found a secret room in Yuno's house. On a whim, he opened the door, causing a massive shift in the future that even shook the Cathedral. In contrast to Muru Muru's panic, Deus was pleased by the drastic change, calling it "a second miracle" after he had twisted causality to bring the twelve participants of the Survival Game to Sakurami City. As the shock to the timeline subsided, the God of Time and Space mused that he was right to have chosen Yukiteru for the Survival Game.

When Keigo Kurusu killed Karyuudo Tsukishima and betrayed the Future Alliance much earlier than planned, Deus commented on the "third miracle" before realizing that Muru Muru had manipulated the Fourth into action. While Muru Muru dodged his attempt at punishing her, she admitted to motivating Kurusu into action ahead of time in an effort to speed up the game, reminding Deus that they had very little time to find his successor before his death. While Deus accepted Muru Muru's logic, he regarded his servant with much more caution from then on, especially when she offered to make a bet with him.

After the Apprentice Users made their appearance, Deus contacted Yuki (and possibly the other participants) to let them ask questions about the new diary users.

When Yuki's mother is killed by his father, Yuki asks Deus to revive her, to which he says he can't, citing the loss of his power as the day of his death draws nearer. He is later seen talking with Muru Muru after Minene's attack on John Bacchus, before dismissing her as he went to rest. Deus is soon visited by Minene in his resting sphere, who asks him about John's Future Diary; accordingly, he reveals the nature of the Watcher Diary and relates how he collaborated with John Bacchus to create the Future Diaries. Deus also takes this opportunity to transfer some of his powers to Minene so that she could stop Muru Muru's scheme to let Yuno win the Survival Game, expressing his suspicions that both Muru Muru and Yuno secretly hailed from the First World where Yuno had already become god. Before returning Minene to her world, he sealed the memory of their meeting within the depths of her mind, intending it to return when she needed to take her role as his trump card.

By the time of John's death, Deus's condition had degraded to the point where the world was starting to collapse. At this time, he was visited by Aru Akise, seeking to confirm if it is possible to resurrect the dead. Contrary to what he implied to Yuki, Deus admitted that he can revive the body of the deceased, but not their soul. He then stopped Akise from leaving, revealing his true nature as the Observer before commenting that he has outlived his role. Slowly vanishing into the Akashic Records, Akise tried to prove that he has a will of his own; Deus calmly and easily disproved each of Akise's arguments, almost destroying him completely until Kamado Ueshita granted him an Apprentice Diary of his own. Amused that Akise was indeed capable of something outside his assigned role, Deus let him live on his own account.

Shortly after his meeting with Akise, Deus's body finally collapses entirely, leaving behind a core which would last long enough to grant godhood to the winner of the Survival Game. In this state, Deus warns Muru Muru that she must allow the game to run properly, as she's restrained by her seals to do so; however, his earlier suspicions proved correct. The Muru Muru that had assisted him throughout the Second Survival Game was actually serving the First World's god: Yuno Gasai, who had similarly replaced her own Second World counterpart in order to spend more time with Yukiteru. As such, Muru Muru was not bound to obey Deus's will, and thus continued with her own plans.

During the final battle, Yukiteru received assistance from Minene, who had survived her apparent demise in the battle against the Eleventh when Deus's parting gift activated. With her restored memories and newfound abilities, the former Ninth was able to bring Yukiteru to the third world that Yuno created in an attempt to repeat the Survival Game once more. Deus's core is eventually taken from Muru Muru by her second world counterpart, who bequeathed the core to Yukiteru after he won the game.

The Third World
The third world's version of Deus is approached by John Bacchus, whose Watcher Diary had gleaned information from Yukiteru's Future Diary after his arrival from the second world. Learning of his eventual death and failure to achieve his goals, John convinced Deus to cancel the Future Diary project, therefore nullifying what would be a third Survival Game. As Deus was still in need of a successor, he and John began pondering alternative options for finding a suitable candidate.

When Yuno unlocked the first world Muru Muru's prison, Deus personally stopped the third world Muru Muru from pursuing her further. He explained that the first world's Muru Muru had viewed the preserved memories of her incarnation of Yuno, seeing the trauma that the girl had suffered in the past two iterations of the universe. As a result, Muru Muru had realized the depth of her own mistakes and sought atonement; furthermore, Deus believed that Yuno's ability to remember and pursue Yukiteru through three separate timelines was a manifestation of fate. As such, he allowed the first world's Muru Muru to transfer "her" Yuno's memories to the third world Yuno before releasing her to assist his Muru Muru in bridging the gap between dimensions.

When Yuno broke the dimensional barriers between the third world and the second world, Deus observed her reunion with Yukiteru. Since both of them had won a previous Survival Game, he happily named Yukiteru and Yuno as his successors as joint gods of the third world. It is implied that this announcement either killed Deus shortly afterwards or simply designated the two of them as the ones who would receive his core following his inevitable demise.

Trivia

 * Deus Ex Machina is Latin for "God from a Machine" or "God of the Machine". In fiction, it is a term used to name a plot device whereby a seemingly unsolvable problem is suddenly and abruptly solved with the contrived and unexpected intervention of some new event, character, ability, or object; thus saying "God made it happen" with no further explanation. This could be a reference to Deus's actions driving the plot of Future Diary, particularly when he directly interferes with the Survival Game; however, it may also be a reference to his machine-like appearance or his pivotal role in the maintenance of reality.
 * In the English version of Future Diary, Deus occasionally uses the phrase "wheels within wheels" to describe his plans.
 * Deus' theme song is "Egoist" by Yousei Teikoku. Unlike most of Future Diary 's OST, this song was never used in the series.
 * In the third opening of Future Diary (the one used in Future Diary Redial), Deus removes his face to reveal Yukiteru's head beneath it, alluding to the results of the Survival Game in the second world.