Three of them were created. The first one was created by Obake when he was a young student, but the experiment failed and blew up on his face, sending him to hospital. The remnant of it was kept by Professor Granville as a memento, as well as a reminder of her mistake of not setting limits. She had kept it as a paperweight sculpture on the desk in her SFIT office, before it was stolen and later destroyed.
Krei Tech and many other corporate tech business tried to create energy amplifiers at one time. Alistair Krei attempted creating it by hiring the best possible scientists, but all attempts only caused fire within the warehouses they were being made. One of the destroyed remains were the inspiration and foundation of Hiro's research in creating his own Energy Amplifier.
The third one, successfully invented by super genius Hiro Hamada, is a device that initially was intended as part of Hiro's final project, but Obake stole it as part of a dangerous weapon. Hiro eventually retrieved his device and received a passing grade for his successful ingenuity. Hiro turned the device over to Professor Granville who locked it in the office vault for safekeeping.
All three were meant to exponentially multiply the output of any power source. Obake's amplifier managed to do this, but not at a huge magnitude, while Hiro's amplifier could create a star from all the energy.
The items only seem to work on gigantic machines such as Kentucky Kaiju, while smaller machines overload with the energy and explode.
Obake first hired Mr. Yama to obtain back his amplifier. Later, when Yama met Hiro Hamada, he threatened the boy until he saw his SFIT ID card, so he blackmailed him into obtaining the amplifier (now kept as a paperweight in Granville's desk) for him in exchange for Baymax's body which he had captured earlier.
Hiro asks Fred for help, and so both devise a plan to copy Granville's ID to enter her office. After they succeed, Hiro takes the paperweight and notices it's heavier than it looks. Both go back to Yama's office at Good Luck Alley, where they give Yama the item, but instead of letting them go, Yama calls his bodyguards and they throw Hiro and Fred in a safe room.
Soon, Go Go Tomago, Wasabi and Honey Lemon find out what happened because Baymax's programming being kept in a computer told them about it, so they break into Yama's office and defeat all the henchmen, then take Hiro, Fred and the Baymax body away with the help of Heathcliff. Upon returning to the SFIT, the team get angry at Hiro, but he remains calm and shows he managed to steal the paperweight back, thus he returns it to Granville's desk.
Yama however managed to duplicate Baymax's body and used it to create a clone army. Obake commanded him to obtain the item again and not fail this time, so Yama used clones to attack the city while he and some others went to the SFIT to get the sculpture.
Hiro and Baymax find Yama at the SFIT because Hiro was building a new armor for Baymax while the rest of their friends fought the clones in the streets, and one of the clones destroys Baymax's vinyl cover, but then Hiro makes Baymax blend in with the clones because he realized he had the same appearance underneath. Baymax enters Granville's office and takes the sculpture, but soon Yama and other clones get inside as well. Before Baymax can escape with the item, Yama drops a book on his head and causes Baymax's healthcare programming to activate, which made Yama realize Hiro was there, so he took the paperweight while his clones attacked Baymax.
Hiro then enters and launches Baymax's rocket punch at Yama, which makes him drop the paperweight and break, then both see it release a green light and the item attaches itself to one of the Baymax clones, causing it to overload with the sculpture's energy and explode. While Hiro tried to save Baymax from falling out of a window, Yama put the item in his pocket and ran away.
During his escape, Yama calls Obake asking why he didn't tell him about the item's true nature, but Obake said he shouldn't be asking questions and simply do the job. After hanging up the call, Yama's pocket is burnt by the item and it falls on an escalator, making it overload as well and causing Yama to fall. The sculpture then attaches itself to a train and causes it to go far faster, but fortunately Hiro and his team stop the train, and then Hiro and Baymax take the item up above to finally blow it up.
After this, the team decide to become superheroes and name themselves Big Hero 6, but at the same time, Obake investigates about them for having foiled his plan.
In the episode "Mini-Max", Granville begins acting suspicious and Hiro notices this, remembering the paperweight item and making him question Granville's actions. When both were stuck in a classroom due to an attack by hacked Security System Robots, Granville revealed part of her backstory with Bob Aken about the accident with Aken's amplifier.
Six months after the destruction of Obake's amplifier, at the SFIT's semester's end, Obake has finished a machine to attempt wiping out San Fransokyo but still needs an amplifier to charge the machine, so he lays out a plan to involve Hiro into creating one.
Knowing so much about Hiro, he correctly makes him miss out his project planning to fight Globby for a Krei Tech briefcase. This in turn, makes Hiro return the briefcase to Alistair Krei, revealing it was also a failed amplifier attempt by Krei Tech's scientists.
Hiro then decides to be successful at creating the amplifier despite being considered impossible, so he starts focusing on it and leaving his friends and superhero work behind. Baymax however advises it is too dangerous and could result wrong in many ways, but Hiro ignores him. Granville is also concerned about Hiro building this due to Bob Aken's fate years before, so she immediately tells Hiro that his project is rejected. Still, Hiro thinks he can prove her wrong and make it work.
Upon finishing the amplifier, Hiro tests it on his computer, his cell phone and a vending machine, although all tech overloads with energy and nearly blows up. Hiro also hides the amplifier from Granville, intending to show it at the SFIT's Open House Expo for the semester end to surprise her. When Fred tells Hiro that he ordered a new Kentucky Kaiju mech, Hiro decides to test it on the gigantic robot to see if it could tolerate all the energy. The test is successful, and so Hiro saves the amplifier back at his SFIT lab.
The day of the presentation however, he is alerted by Baymax that Obake was nearby, so Baymax convinced him to go get him and miss the presentation because it was for the greater good and Tadashi would have wanted it. Upon arriving to Obake's presumed location, Hiro and Baymax instead find a robot decoy which distracts both while Globby, Noodle Burger Boy and Momakase attacked the SFIT and allowed Obake to steal Hiro's amplifier.
Afterwards, Granville reveals that Obake was her former student and that he also tried to build an amplifier of his own, but the experiment failed and was what turned him into Obake due to the injuries.
Back at Lucky Cat Café, Hiro notices Baymax isn't reacting to his pain with his healthcare protocol, so he opens up his chip port and sees an Obake Chip inserted into him. Baymax then becomes aggressive and takes Hiro to Obake's lair, where Obake reveals he wants to become Hiro's mentor and that both are alike.
Since Hiro refuses to obey Obake, he is thrown into a cell and Obake gives Noodle Burger Boy the amplifier to turn on the machine and achieve his goal, but Globby learns that the plan is too insane and decides to betray Obake and help Hiro escape.
Globby and Hiro go back to Lucky Cat Café to get Hiro's armor and warn the rest of Big Hero 6, and since Baymax was still under Obake's control, Hiro uses his Skymax robot to fly to the lightouse where Obake's machine was built and remove the amplifier from it. With Skymax's help, Hiro retrieves it and joins his friends, but all see that the machine had become self-sustaining regardless, so Hiro has to think another way to stop the machine. He quickly remembers Kentucky Kaiju and reasons that a force of equal strength would stop the shockwave created by the machine, so he, Fred and Mini-Max set out to stop the plan inside the kaiju.
After managing to counter the shockwave and putting an end to Obake's plan, Obake becomes too despondent to see his dream fall apart and decides to let Baymax go while he stayed in his crashing lair waiting for his fate.
Finally, Hiro turns over the amplifier to Granville after having learned from his mistakes, and Granville locks it inside a safe at her office to keep it out of the wrong hands, but still gives Hiro an "A" for his final project.
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