In the years since the Third Kaiju War in 2060, Earth has enjoyed a long period of peace. Resources and territories were no longer a cause of conflict, as the kaiju wars essentially forced the advancement of technology, and before long humanity built a space fleet, reverse-engineered portal technology from the Precursors used to travel to planets and systems far from Earth for colonization and resource mining, as well as put aside the petty differences which splintered humanity from one unified community altogether.
Since then, the United Nations of Earth has become the central government of humanity. Jaegers and effectively the PPDC have become the main military force of the United Nations Defense Force, and the world was at peace.
Then, in 2137, another breach opened on Earth. But unlike other instances, it was on land, and what came out were not multi-ton silicon-based lifeforms known as Kaiju; they were humans who resembled the soldiers of Ancient Rome. Unknown to these soldiers, however, was the might of a species who survived titanic horrors with monsters of their own.
Matias Cox.
Everyone in New York City knows who he is: He once made headlines as potentially the next de facto leader of the PPDC. His coordination skills were on par with the legendary Stacker Pentecost, his partner Clark Avery just as incredible. He was also recently featured as one of the youngest PPDC Rangers to have said title, at the age of 25. He was heading back home towards Gramercy.
At least, he would have, had a breach not been detected in the middle of Central Park.
NYPD has already formed a perimeter around the park with their Minigers (Mini Jaeger, most of which are produced for civilian use and public safety, or in the UNDF's case onsite tactical support for the full-fledged Jaegers), each of them 12 meters tall standing in front of the non-armored police, just as Matias approached them.
Upon his first assessment, it was already obvious that it was not the Precursors who opened this breach; why would they put an Ancient Greek-era structure around it? Considering the size of the Kaiju, even the smallest one would not fit through this 30 x 20 meter opening.
One of the officers noticed him and saluted him.
"At ease, officer. The PPDC is sending over Cardinal Phoenix just in case." Matias looked to his left, seeing a vacant NYPD Miniger. "May I?"
"Of course. Go right ahead." The Officer, named Edgar, stated.
The Miniger's systems wasted no time to boot up, just in time as numerous figures stepped out. They were mostly human, but others that came through with them looked less human, moreso like the demi-humans of any fantasy story ever written.
When enough of them passed through, the one who seemed to be their leader shouted an incomprehensible phrase, and began to charge.
Matias and co. didn't need any orders to know what to do.
Since the Second Kaiju War in 2036, the PPDC has commissioned the construction of airborne Shatterdomes, literally supermassive spaceships carrying dozens of Jaegers each, in patrol over the skies of Earth, Mars, Jupiter, and every human-controlled planet.
Jaeger booster fuel relied on the extreme reactivity of Kaiju blood to rare earth elements. Such a discovery kickstarted industries who synthesized Kaiju blood, and its mass production only helped to deploy these Jaegers to any location on their host planet in less than an hour, in a process people affectionately call, which later became its main calling method, Jaegerfall.
After the Third Kaiju War in 2060, the UNE have also made efforts to widen and reinforce every major road to be big enough for Jaegers to walk through them. It at least helped to reduce collateral damage whenever Jaegers fall from the sky every now and then for deployment.
Near the coast of New York City, in the Atlantic Ocean, was the mobile Shatterdome known as the UNDF Dart, where a massive red-silver Jaeger known as Cardinal Phoenix, itself standing at 290 feet tall and weighing 7450 tonnes stood inside Bay 16. Already, its pilots Tamara Gilbert and Vicky Alya were inside the Con Pod.
"UNDF Dart, this is Cardinal Phoenix. Ready for action."
"Copy, Cardinal. Standby for Jaegerfall."
The hatch above the Jaeger opened, and then its own thrusters activated, propelling the metallic behemoth into the skies and towards New York. The two pilots stayed still as autopilot set a course for them to land directly inside Central Park.
Once it did, NYPD eyed at the machine momentarily before resuming fire on the invading Roman army, or some legion of soldiers that resembled such. Cardinal Phoenix began to fire plasma bolts from its shoulder-mounted turrets, shooting down any of those wyverns alongside UNDF Air support. Said soldiers didn't even try to think what manner of weapons such a massive golem could use before they either surrendered or frantically attempted to run back through the gate.
Before long, the invaders were no more.