- "Oh holy father, holy Brother, holy master... My sacred mission is at last complete. With these two hands, mankind is saved. I am your will made flesh. In your name, I give thanks."
- — Dio, revering Brother, Free the Soul's founder
Dio is shown to be highly irascible, mean and insensitive towards the other players. It is later revealed that Dio, while not the mastermind behind the game's events, is in fact its secondary antagonist; he is the leader of the Myrmidons, the military branch of the religious terrorist group Free the Soul, and he is working on behalf of the game's/series' main antagonist, Brother. He is responsible for murdering Akane Kurashiki in the Yellow/Magenta routes, and he is responsible for planting the Antimatter Bombs in the Cyan routes, all in the name of his undying loyalty to Brother.
Dio is a young man with turquoise eyes and long blond hair, which he keeps in two braids. He wears a red coat with gold cuffs, a black top hat, gray pants, and black boots. Like all of the players, he wears a bracelet on his left wrist.
It is later revealed that Dio is a clone of Left, and so he strongly resembles Left.
Dio is selfish and his course of thinking causes him to almost always pick betray. His cold personality is also shown in the routes where Quark disappears. He openly says that he "doesn't care about some kid he doesn't know" to Tenmyouji and even suggests the possibility of Quark being dead. He also tries to keep the other participants' BP as low as he can possibly get by instigating them to betray each other, resulting in both parties gaining nothing. Similarly, he tries to get others to ally with him, even to point of endangering their life, such as Sigma in Quark END, when he will resort to holding Quark hostage to leverage Sigma who has 1 BP into picking Ally. If Dio is paired with Quark in an AB Game, Dio tends to blame him, saying he chose Betray and he's "full of shit". He doesn't get along with Quark, Tenmyouji and Alice. Phi thinks he's an asshole.
His apathetic and misanthropic behavior towards the other players stems from his belief that humanity is evil, corrupt and undeserving of his respect. Many of his actions can be attributed to him genuinely believing in what he is doing as the leader of the Myrmidons and a member of Free the Soul, rather than malevolence. In his own words, "I'm a hero. I was sent here from far away to save mankind." Dio's thoughts and values are likely the result of someone who has been heavily indoctrinated into this Myrmidon system by this religious cult, possibly at a young age.
Dio is extremely irritable, irascible, callous and impatient. He tends to tease and insult every player often, and as a result is very disliked by mostly everyone. He is sadistic, as shown when he gleefully murders Tenmyouji and Clover in the Luna route, and does the same to the old woman, and laughs aloud with joy when he threatens to murder eight others with the bombs. He also tends to say what's on everyone's minds (even the player's at times) but do not want to vocalize.
To a fault, Dio is rather arrogant as well. In three of the routes, Dio proudly says aloud the bomb passcodes and confesses to being a Myrmidon just to rub it in people's faces, unaware that he is giving them the information they need to defeat him in the other timelines. Additionally, Dio is also cowardly and not always physically adept. Sigma, K and Alice all tackle him to the ground, Clover is able to help incapacitate him, Phi outruns him and Tenmyouji knocks him to the ground.
Dio is also shown to be cowardly and, although he is loyal to Brother, he does not seem willing and ready to die for him due to this cowardice. In the Sigma and Phi endings, when he is exposed as the one who planted the bombs, Dio refuses to detonate the bombs by his own hand and some hesitation is seen in his eyes when Tenmyouji taunts him to detonate the bombs. This gives Tenmyouji the chance he needs to knock him out. Dio was willing to consume a suicide capsule to ensure that the others couldn't get the bomb passcodes out of him, but even then, it should be noted that he only did this once Alice began to torture him.
Despite this, Dio is still determined to accomplish his goals and will resort to the extremes to achieve them - even if it means suicide. Dio is also easily the game's most profane character, and he doesn't stop being this even around Quark. However, Dio is not outright irredeemable; he apparently once saved a kitten on a rainy day, despite being more of a dog guy, and he also is willing to pick Ally on a few very rare occasions. He was also once romantically involved with an unnamed woman, but this "corrupted" him, and he joined the mission to show Brother he can redeem himself.
Dio came from the 4th generation of the Myrmidons. He was one of Left's clones, who were created by a man called Brother, the leader of the religious organization Free the Soul. Even though everyone was supposed to be created equal, there was some random deviation, and other factors could influence the clone's development. Dio was the best of his generation, so he was chosen to lead the Myrmidons. Dio keeps the fact that he is part of Free the Soul extremely private.
His mission was to infiltrate Rhizome 9 on the Moon on the day the Nonary Game: Ambidex Edition took place, and participate and win the Nonary Game. In case he failed to kill Akane Kurashiki, his emergency plan was to blow up the whole facility by planting and detonating four antimatter bombs inside the building. He would hide the bombs on his back and the detonator in his hat. Dio was also equipped with a transmitter to keep in contact with Free the Soul and Brother.
Brother is an esper who knew that Radical-6 would be used in the Nonary Game: Ambidex Edition, so Dio was infected by the group before entering Rhizome 9.
In both cases, the ultimate goal was to stop the AB Project. When he was given his orders during the briefing, he thought of it as a chance to prove his loyalty to Brother and was determined to succeed in his mission, no matter what.
Virtue's Last Reward
On January 25th, 2074, Dio, on Brother's orders, infiltrated Rhizome 9 to stop the AB Project from succeeding. He entered through the Number Nine Door and hid behind one of the AB Rooms in Warehouse A. The first one out was Akane Kurashiki. Depending on the timeline, Dio either:
- Kills Akane with a knife under the "TWO MILKMEN GO COMEDY!" graffiti, takes her bracelet and wears it after wiping the blood off with a handkerchief. He then throws his handkerchief-wrapped knife between the two AB Rooms on the right to hide it. He then enters the AB Room where Quark is and waits for the game to begin. Luna moves Akane's body into the sixth AB Room and keeps Akane's body a secret due to her orders.
- In the timelines where Dio fails to kill Akane (Cyan door), Phi knocks him out and Akane removes her bracelet using Zero III, then puts it on Dio's left wrist. His unconscious body is then moved to the same AB Room that Quark is in. Akane also adjusts his bombs so that their timers are synced to Radical-6 time. She changes the password of the first bomb to BQZ RGJ DXR (Crash Keys), presumably because it is the only bomb password which Dio never reveals in any timeline. Akane then plays as K while Kyle's body sleeps in a treatment pod in the B. Garden.
Dio escapes the room with Quark and they meet with the other players. He is paired with Quark for the first round of the AB Game. Sometime after this, he probably places Bomb #0 in Warehouse A between the AB Rooms, and then proceeds to place the rest of the bombs.
In the cyan door timelines, Dio planted four antimatter bombs in the facility numbered 0-3 and blew up the facility.
In the two timelines where Dio was revealed to be the culprit behind the bombs, he showed the activation device, only for Tenmyouji to knock it out of his hand. However, the device, separated from Dio by 1 meter, automatically activated. Dio then proceeded to attempt suicide with a cyanide pill, but was ultimately restrained by Sigma and later sedated by Luna with Soporil ß.
In a third timeline, where Dio accidentally revealed himself to be the culprit under Sigma's questioning, he showed the activation device but was outsmarted by Alice and Clover, the latter of which threw the activation decide to Sigma. The device, being separated from Dio by 1 meter, automatically activated, and he successfully managed to consume the pill and die in Alice END.
He is also killed by K in both Luna's and K's ending because he killed Akane. In Clover END, Dio kills himself due to Radical-6.
One pathway that can quickly teach the player of Dio's true malice is the Quark END pathway. In this pathway, Dio is a solo with 6 BP paired up with Clover, who has 6 BP, and Sigma, who has 1 BP, going to the laboratory. After the only medicine that can save the incapacitated Quark is discovered, Dio takes it hostage and threatens to destroy it if Sigma, despite having only 1 BP, pick "Ally" so that he can pick "Betray" and go up to 9 points. If Sigma concedes, he is almost killed and Dio escapes, and in the other pathway he indeed shows himself willing to destroy the medicine he took hostage if Sigma refuses.
Dio's ending occurs in a timeline where Akane was killed. Dio investigates the Crew Quarters with Tenmyouji and Quark. After betraying Tenmyouji in the first round of the AB Game, Dio's BP becomes 6. He blames Quark for betraying Tenmyouji and that he should watch his grandson more closely. He even warns Tenmyouji that Quark could be "a born conman".
For the second round, he is paired with Phi and goes through the blue door with Luna to the Pressure Exchange Chamber. While there, he learns about the pressure of the facility from Luna. After leaving the PEC, Dio opens his AB gate early. After a couple of minutes, Alice and Clover arrive, telling them that Quark is missing. They go off to search for Quark, but Dio runs into Sigma and Tenmyouji. Dio accuses Quark of being Zero. Before Tenmyouji can react, Phi appears, telling them they found something in the Crew Quarters. Sigma, Dio, and Tenmyouji follow Phi to the Crew Quarters and discover Alice and Luna dead.
Phi says Clover discovered them, and Dio immediately says that Clover is the killer and that she killed Alice because of them knowing each other before the game. K states that Zero knocked them out and killed them, while they were asleep. Dio also points out Quark as a suspect because of his disappearance or that he was possibly killed as well, which angers Tenmyouji. An announcement for the AB Game rings out saying only ten minutes until voting ends. Since Clover and Sigma both have 6 BP, Dio gets excited to see the results of the round.
In round 2, Dio and Phi betray Luna and reach 9 BP, enough to escape. Dio tries to open the Number Nine Door, but Phi stops him to see Sigma and Clover's results. At the end of the round, Sigma has 9 BP. He manages to escape the facility with Phi and Sigma despite Tenmyouji and K trying to stop them. While escaping, he talks about Charles Darwin's survival of the fittest theory and how it applies to the Nonary Game. Once through the Number Nine Door, Sigma, Phi, and Dio end up in another PEC chamber. The trio must first wear hazmat suits get depressurized in the pressure exchange chamber and arrive at the surface of the Moon. While in the PEC, Dio mentioned that he was a hero to Sigma and Phi and that he had fulfilled a mission to save the world. Upon exiting Rhizome 9, Dio slipped by them and went to the transmitter he had hid beforehand to try to contact Free the Soul, but was confronted by Phi about him being associated with the terrorist organization.
Dio eventually admitted to being a Myrmidon, and tried to kill Phi with a rock, but was quickly stopped by Sigma, who had heard most of their conversation on the radio, with the rest being static. Dio told Sigma and Phi everything about his life and that in all of his life, he had only ever once been punished breaking their laws. He'd come into contact with one woman, who was someone considered to be unclean, and was declared corrupted. Even though he was punished harshly and purified his soul, he claimed that his dishonor remained and that completing his mission would atone for that dishonor. He informed Sigma that his entire purpose was to be part the foundation of Brother's new world.
As Dio thought they had no use for it, he told them the deactivation code for bomb #0, since Phi had asked him about it earlier. Dio then reluctantly escorted them to one of the other Rhizome facilities, where he knew a few acquaintances.
In an alternate past, Dio attempted to kill Akane Kurashiki to enter the game. However, he was knocked out by a flying kick from Phi, which was possible due to the Moon's weak gravity. Akane then took his knife and gave Dio her bracelet, thus preventing much of the future timelines. Dio was then placed in the same AB Room as Quark and Akane took the place of K by putting on his armor.
Due to the multiple time jumps by Sigma and Phi, all 4 passwords were ultimately gathered and the 4 bombs were defused. Dio was unconscious and had been handcuffed to a sink pipe in the Infirmary. All 8 other players decide to leave him there, as they proceed through the number nine door.
Another Time END
After Sigma's and Phi's consciousnesses jumped back into April 13, 2029, Dio soon woke up, but was quickly put to sleep with Soporil ß by Luna.
According to the answers, as the AB Project had succeeded, Akane no longer saw him as a threat, and it is implied he was released.
Zero Time Dilemma
Although Dio is not mentioned in the game, it is indirectly revealed that Dio was just a pawn of Brother, whose true name is Delta, in order to help out with the AB Project. It is revealed Delta and Akane met decades before Virtue's Last Reward in 2029, and this is most definitely when the duo teamed up to work on the AB Project, with Delta's true intention to stop a religious fanatic. Akane intentionally let Dio into the Nonary Game: Ambidex Edition, as a sense of danger would help Sigma and Phi learn how to SHIFT.
- "Where are you, you little bastard!? Too scared to come out and face me like a man?!" (to Zero III)
- "FUCK THAT! We aren't gonna open SHIT! You can take your LAME-ARY GAME and SHOVE IT UP YOUR ASS! If you think we're just gonna swallow your psychotic crap and play along, you've got another thing coming, you smart-ass little rodent! Shut up!" (to Zero III)
- "That little piece of shit... If I could just get my hands on that little fucker, I'd squeeze him till he popped." (on Zero III)
- Alice: "We ran into them a little a bit ago. Well, not literally, of course."
Dio: "I dunno, with a prow like that, I imagine you run into a lot of things."
- "Then you're telling us we should just prance off and ignore the INCREDIBLY DEADLY BOMB that is probably going to KILL US ALL?!" (to Alice)
- Alice: "Oh God... I never thought I'd have to put up with Dio again."
Dio: "Well, you just didn't think hard enough then? Sooner or later, everybody puts up with Dio!"
- "Oh gimme a break! How can you just sit around here talking?! Are you fucking kidding me!? One of us is a KILLER! I can't think of a better reason to make a fuss!"
- "This game isn't about compassion, and it's not about being clever. It's about one thing: how well you can manipulate people to your advantage. How unfair you can be."
- "You both crossed a line you weren't supposed to cross. You betrayed your friends. Am I right? I'm right. But you didn't have a choice, did you? You had to survive! Isn't that the way an animal thinks, though? Don't get me wrong, I see the logic, but it's kind of... animal logic. Still, you made your bed. Now you've gotta lie in it. If you're gonna be an animal, BE AN ANIMAL. Own it! The losers, the weak? Throw 'em away! That's how nature works, my friends -- that's life at its most pure! You get me?" (to Sigma and Phi)
- "No one has more gentlepoints than me. You think someone of my stature would resort to VIOLENCE?! The nerve!"
- "You bitch! Goddamnit, Phi! Open this fucking door!"
- "Hmph. Another dude... This place is turning into a real sausagefest." (to Sigma)
- "It's a dirty magazine... Just look at those rings on Saturn. Don't they excite you?" (to K and Sigma)
- "Asshole... Better hope I don't have rabies, you self-satisfied old turd." (to Tenmyouji)
- "Hey, Sigma, is this chick... simple or something?" (about Clover's poor lever pun)
- "YOU FUCKING BITCH! You're not getting out of here!" (to Clover escaping through the Number Nine Door)
- "Just hurry up and die, you senile old fuck!" (to Sigma)
- "I'm not going to let my sacred mission get fucked up by some self-righteous idiot!" (to Sigma)
- "At least one of you is appropriately ignorant..." (to Sigma and Phi)
- Clover: "Are you going to beat us to death or something?!"
Dio: "Ugh. No, nothing so tasteless."
- "So! I suggest you start screaming for help... now. Unfortunately for you, just about all the rooms in this place are behind at least two nice, thick doors. So unless they're pretty close, nobody's gonna hear you scream. Well, I'm off to the floor B warehouse, okay? Enjoy your last 25 minutes. Later!" (to Clover and Tenmyouji)
- "Come on, what is this? Are you high?"
- "Nice try, but that's some bullshit totalitarian logic. I don't think so."
- "Who the fuck do you think you are?! None of that has anything to do with me!"
- "Anyway, I think it's time for me to be moving on... to the next world." (before attempting to swallow a cyanide suicide pill)
- "You can do whatever you want to me, you FUCKING COWARDS! You're STILL GONNA DIE! Go ahead, tell yourselves you can fix it! Run around like IDIOTS before you get blown to ATOMS! Serves you FUCKING RIGHT! You're gonna BURN!"
- "I'm a hero. I was sent here from far away to save mankind."
- "Free the... Soul? What's that? Some kinda hippie shoe company?"
- "Whoa there. I like my women a little feisty, but you're taking it a little too far, sweetheart. Tone it down." (to Alice)
- "My body will... be a part of the foundation of a... bright future... Such a... beautiful... world... May Brother live... in everlasting... glory..."
- In the Cyan door route (pictured right), Dio foreshadows one of his possible fates. He also says this on the route to K END, in which this occurs.
- On the cyan door routes, in which backstories are revealed after the first Chromatic Doors, Dio claimed to be a circus ringleader, as is reflected in his outfit. The backstories revealed are cut from the other routes due to Akane's (known then as the "old woman") corpse being discovered.
- Sigma only goes through an escape room once with him in the game.
- Dio's name possibly comes from Dionysus, the god of wine in Greek mythology. Alternatively, the Italian word for "god" is "dio".
- On Luna's route before the second Ambidex game, Dio says that he has a lot of Gentlepoints, which is a reference to the Professor Layton series.
- Dio is the only character that doesn't lose any BP during any of the routes; he almost always picks Betray, and when Quark outdid him and picked Ally against his will, he still gained BP.
- The only person Dio did not willingly Betray was Luna, unless she was already dead, because he views her as beautiful. He is also nicer to her than to the other players.
- This could have been partially because of her physical similarity to Diana, the biological mother of Free the Soul's leader; however, given the contradictions between Brother's "backstory" (as told by Dio) and the events that took place in ZTD, it is unlikely that he knew of Diana's existence, let alone her connection to Brother.
- The only person Dio did not willingly Betray was Luna, unless she was already dead, because he views her as beautiful. He is also nicer to her than to the other players.
- Dio was restrained by 3 different characters while squirming on the ground over the course of the game. One instance was in the K END, where K forced him to the ground once Sigma had deduced that he was the killer. Another instance was during Alice END, where Alice forced him on the ground while he interrogated her. In two pathways -- Sigma END and Phi END -- Dio is forced to the ground by Sigma.
- Dio's cover is almost blown when Zero III says that Dio already knows the second way to remove his bracelet (death), prior to the AI telling the rest of the group about the function of the bracelets. This implies that Dio was involved in watching someone's bracelet release through death, which refers to him killing Akane Kurashiki.
- Zero III says this even when Akane is not killed (cyan door routes), which may make it seem like a continuity error. However, considering Akane is an Esper and knows how the entire game will play out, she is probably just trolling Dio. Similarly, Zero III also calls Clover "Cleaver" likely in reference to the axe ending of 999, despite that the axe ending isn't the true canon ending.
- Dio says the F word on 39 different occasions in Virtue's Last Reward, more than three times the amount that Santa says it in Nine Hours, Nine Persons, Nine Doors (11 times). He is the most profane character in the series.
- In Luna's route, Dio handcuffs Clover and Tenmyouji to a sink, which prevents them from participation in the Nonary Game (the punishment for not participating in the Nonary Game is death). Originally, Dio was meant "to do something even more messed up to Clover" which included Dio's knife, however, Uchikoshi's president opposed this scene due to "ethical reasons," so the scene was quickly changed. It can be theorized that Dio would have:
- Given Clover his knife and told her that she could have the option of slicing her hand off to escape the handcuff.
- Given Clover his knife and told her that he would free her if she tortured or killed Tenmyouji with it.
- Dio would have tortured her with his knife or murdered her by stabbing or a throat slitting.
- Some fans have theorized that Dio would have done something sexual to Clover such as raping her. However, it is extremely unlikely considering that Tenmyouji is next to her, and that Free the Soul practices sexual purity and is meant to "divorce the soul from lust", and that Dio already got into trouble for being involved with a woman earlier.
- Because of the above trivia point, it is extremely ironic that Dio is sedated and handcuffed to the same sink in the true ending.
- Dio is the only male character in the game to be paired up with Sigma. This occurs after the 5th round of the AB Game in Phi END in which he is a cyan pair.
- Uchikoshi once teased that Dio would appear in Zero Escape: Zero Time Dilemma, but "not as the man you know". Nothing ever became of this, however, as this was a scrapped plot point.