Corruption

It had been many years since Tagiru and Gumdramon defeated Quartzmon and every reality and timeline has been restored, but during that final battle, they all learned of different worlds based around the Digital World.
From the Digidestined universe to the Data Squad universe, Tagiru decided to become a Time Keeper to make sure the timelines are well in balance.
He has learned much about each universe's stories and history and how they are all different.
20 years passed since then, and Tagiru and Gumdramon were the last Fusion Fighters left as many had retired.
Outside his huge base in the middle of Japan, a young man with red spiky hair, yellow goggles, a red and white jacket and blue jeans was running towards it with a yellow dinosaur Digimon by his side.
"Tagiru!" The young man called, closing in on their hideout.
"Oh boy, I love it when Tagiru and Gumdramon call us." The yellow skinned Digimon said, before stating. "And I love all these Digimon stories of the other worlds and all. They're awesome!"
"Me too!" The young man replied.
"Let's go!" He shouted, as they charged through the door.
Meanwhile, in their chamber, a now grown up Tagiru and Gumdramon were looking through a scroll looking quite puzzled when the door flew open.
"Tagiru! We're here!" Tagiru turned to see the young man and Digimon.
"Oh, Spike! GAgumon! Nice for you to come." Tagiru said.
"You two always like hanging about here." Gumdramon added in reply.
"I know. But we love watching the stories of each world through those video scrolls of yours." GAgumon said, pointing to the scrolls.
"Yeah, but..." Tagiru said, looking a bit puzzled.
"What's wrong?" Spike asked.
"Lately these scrolls are glowing with dark purple auras." Tagiru explained, showing him the scroll, which began to glow in a deep dark aura.
"What does it mean?" Spike asked, worried.
Tagiru opened one of the other scrolls to reveal something horrifying.
It was the world of the Fusion Fighters, but Angie, Jeremy, Dorulumon and Ballistamon lay defeated and dead on the ground.
And there was no sign of Mikey or Shoutmon.
"S...Shoutmon." Lunamon whispered before she died.
It was the same in the Data Squad world, most of their heroes were also dead as Thomas, Gaomon, Keenan, Falcomon, Kristy, Biyomon and many others were laying in the destroyed DATS base. 
Lalamon was also seen dead and Yoshi was on her dying breath was also tearing up. "G...give us back...Marcus...A...Agu...mon..."
Before death claimed her.
The Frontier world was also gloomy as Koji, J.P, Tommy and Koichi, also lay dead, while Zoe was near death but before she died, she muttered. "Who was that boy and evil Digimon...and why did he take...Takuya?"
And in the Tamer's world, the area was full of death.
The Hypnos headquarters was destroyed.
Henry, Terriermon, Ryo, Cyberdramon, Jeri, Kazu, Kenta, Impmon and BlackRenamon were lying on the ground, mostly dead, while Rika and Renamon were near death as well, but there was also crying.
"T...Takato." Rika said weakly.
"Guilmon...we failed...forgive us." Renamon said sadly before she and Rika died too.
Spike was horrified at what he saw.
This isn't how it happens.
"Who could have done this?" GAgumon asked.
"Look at the Digidestined's scrolls and find out." Tagiru said. Spike looked through the scroll.
-The Digidestined's world-
Matt, Gabumon, Izzy, Tentomon, Joe, Gomamon, Mimi, Palmon, T.K, Patamon, Ken, Wormmon, Yolei, Hawkmon, Gatomon, Cody and Armadillomon were all dead as well, with Tai and Davis being the only survivors as they held the dead bodies of Sora and Kari in their arms.
Agumon and Veemon, who were holding AquaVeemon's and Biyomon's dead bodies, glared at the opponents who were facing them.
It was Gallantmon, EmperorGreymon, Marcus, ShineGreymon, Mikey and OmniShoutmon, but something was wrong and different about them.
They all had an evil purple aura glowing around them, their eyes were completely red, while black lines trailed their eyes.
Behind them was Quartzmon, Kurata, Myotismon, Devimon and the D-Reaper, the greatest evils known in each world, all of them also glowing in a dark purple aura with the same red eyes.
While an unknown boy with red eyes, black hair, a black jacket, white vest and grey trousers was by their side.
"Devimon! Myotismon! Are you two behind all of this!?" Tai snapped as he and Davis rose, looking angry.
"Humph. I think you should talk to Specter if you want to know." Devimon cackled.
"But this is the end of you, Digidestined!" Myotismon stated wickedly.
"With your Digimon's deaths and your ends, everything will change." The young man known as Specter, said.
"We'll see about that!" Davis snapped, before he shouted. "Veemon! Agumon!"
"Right!" Veemon and Agumon replied as they rose up, getting ready to Digivolve.
However...
"Shield of the Just!"
"Twin Fireball Strike!"
"Glorious Burst!"
"Dragonfire Crossbow!"
The dark Gallantmon, EmperorGreymon, OmniShoutmon and ShineGreymon shot out their attacks and hit the 4 remaining heroes before the dust subsided to reveal Tai, Davis, Agumon and Veemon had been defeated.
Seeing the destruction of the Digidestined, Specter, Quartzmon, Kurata, Myotismon, Devimon and the D-Reaper laughed evilly as nobody was left to stop them.
-Present time-
"What happened to them?" Spike asked in horror.
"That man, Specter, has made a deal with the 4 villains you see before you." Tagiru replied, before he explained. "They plan to change the timelines. First, they kidnapped the heroes of those different worlds. Then they used them to kill the other heroes. But if Tai and Davis go..."
"Everything goes with them, including futures, different timelines, the people and Digimon, you name it." Gumdramon said, finishing Tagiru's statement.
"Oh no!" GAgumon said, worried.
"But there is a way to stop them." Gumdramon said as the 'X' scarred dragon Digimon told Spike and GAgumon. "That's why you are here. We need you to go in those timelines, prevent the other heroes from dying, save the leaders who were brainwashed and help the Digidestined survive."
"And with the other heroes and the Digidestined by your side, together you might stop this maniac, Specter. Will you help us?" Tagiru asked.
Spike and GAgumon looked at each other in worry, but their worry turned to determination as they nodded and turned back to their mentors.
"That guy Specter is trying to destroy the thing we all wanted to protect. And it sounds like he's trying to destroy the things we love to watch and read." GAgumon said.
"So we'll be more than willing to help you guys out anyway we can. Let's make this guy sorry he messed with us." Spike stated in a determined tone.
"Thank you, Spike." Tagiru happily replied. "I know we can count on you. Take the scroll with the Digidestined's death as evidence. And we made a machine that can travel to otiher dimensions."
As Spike picked up the scroll, Gumdramon opened the door to reveal a hover bike and a computer in front of them.
"Take this communicator with you so we can communicate with each other while you are in different timelines and worlds." Tagiru said, handing him a communicator.
"Right. So what are we supposed to do?" GAgumon asked as he and Spike climbed aboard and Spike turned on the ignition.
"You musn't let Angie, Zoe, Rika, Renamon, Yoshi or any of the other heroes die. You must save them and tell them what will happen. Then gather all the heroes and head to the Digidestined's world before Specter and warn them for the upcoming battle. You must defeat Specter, Kurata, the D-Reaper, Myotismon, Devimon and Quartzmon and free Mikey, Shoutmon, Marcus, Agumon, Takuya, Takato and Guilmon from their control. Angie, Yoshi, Lalamon, Zoe, Rika and Renamon can do just that since they have feelings for them. And we must not let Tai and the Digidestined die. I hope you know what to do." Tagiru told them in reply.
"I do." Spike replied, holding up his Fusion Digivice, before stating. "I'll make you guys proud of me."
And then the bike and Spike and Gagumon disappeared, first to the past.
"We're counting on you." Tagiru said to himself as Gumdramon nodded in reply.