Ener - D Ener - D , spelled as Enerdy in " Yu - Gi - Oh ! 5D ' s Tag Force 4 " and " " , known as Moment in the Japanese version ( and sometimes romanized as Momentum ) , and short for " duel energy " , is a form of energy in " Yu - Gi - Oh ! 5D ' s " . It is the ultimate energy generation system that keeps spinning in one direction to create an endless power supply . Ener - D is the source of power in New Domino City that keeps the city running while making the technology for Duel Runner s , Turbo Duel s , and Solid Vision possible . In the dub , its name comes from the word " energy " , but replacing the letters GY with a - D , which stands for dueling . The change may have been due to the fact that in English , the term momentum refers to the product of a body ' s mass times its velocity . Ener - D System . Kaiba Corporation ' s R . R . D . was in charge of this technology ; the lead developers who had begun the research were Yusei Fudo ' s parents , following Dr . Fudo ' s discovery of the Planetary Particles which were essential to making Ener - D possible . Roman described the Ener - D as a near - limitless source of energy that doesn ' t produce any contamination . The Ener - D Reactor is implied to be a Perpetual Motion Machine , and runs at full capacity in order to meet the power requirements of New Domino City . Everything in the city is powered by the Ener - D ; if the Ener - D shuts down the entire city suffers a blackout . Its limit is in its ability to channel excess energy it produces . The appearance of the Crimson Dragon during the duels between Yusei Fudo and Jack Atlas caused the system to exceed its limits . During their first match when the Crimson Dragon appeared , it overpowered the system by dramatically overflowing the energy generation to it . As it was incapable of handling so much power , the system completely shut down , leaving the city in a total blackout . The overflow problem occurred once again during the Fortune Cup , though according to Zigzix it was running at full operation . Apparently some modifications had to have been made to the system , since the 2nd appearance of the Crimson Dragon only caused the temperature and pressure within the Ener - D Reactor to reach critical point rather than cause the system to blackout as it had before . According to Bruno , the Ener - D is self - aware and can read the emotions of humans , and should a human reach the Clear Mind state , they can control that Ener - D . It is later revealed that Synchro Summoning causes the Ener - D to spin faster , speeding up the evolution of humanity in the process . However , if it spins too quickly , it will shift into reverse , creating an explosion like Zero Reverse at a massive scale . In the apocalyptic future Z - one , Antinomy , Aporia , and Paradox came from , humanity had abused the power of Ener - D to control evolution and filled it with greedy desires and emotions to the point that the Ener - D went insane and created an army of Meklord Emperor s to kill all of humanity , and later exploded completely ; these two events completely destroyed the world and humanity itself . The only survivors attempted to stop this apocalyptic future by going the past and erasing Ener - D from existence . In episode 149 , it is revealed that the Meklord Emperor Genocide could be stopped by removing the negative emotions that caused the Ener - D to go out of control and build the Meklord Emperors in the first place , but unfortunately Z - one discovered this too late and couldn ' t stop the Ener - D before it exploded . Thanks to Z - one ' s intervention , the present day New Domino City became aware of the situation , and Yusei created a program known as Fortune , which keeps the Ener - D under control , thus preventing the Meklord Emperor Genocide from occurring . Ener - D Reactor . After the Fortune Cup , the existence of the Original Ener - D Reactor was revealed within Satellite ' s inner grounds . However , according to Rex Goodwin , as it was the first system , it was totally insecure and imperfect when it was activated seventeen years before by R . R . D . . Consequently , the system ' s activation resulted in the major catastrophic event known as the " Zero Reverse Effect " . This was the reason behind the destruction and splitting of Domino City into New Domino City and Satellite . The system was abandoned in Satellite , until it was " found " by the Dark Signers . According to Goodwin , the Original Ener - D Reactor was being used as a door to the Underworld . The system possessed four safety switches located in the B . A . D . area . These were a fail - safe placed long ago after the system was shut down completely . Each of the control units are code - named with the name of one of the Earthbound Immortals and is guarded by the Dark Signer who possess the corresponding Earthbound Immortal card . The main system itself is represented by the Spider mark and is guarded by the leader of the Dark Signers , Roman . Before Roman and Yusei ' s second duel took place , the Dark Signers blew up the Original Ener - D Reactor . As the negative energy was released the two of them , standing above it , commence their rematch . Yusei won the duel but Roman blew up the bridge and Yusei fell into the reactor . Only three of the four control units were activated , because Akiza Izinski ' s Duel with Misty Tredwell prevented her from activating the last tower in time .