Imperial Rim: Kaiju
"The thing about life is that you get used to it. I got used to the worst that xenos and heretics could throw at us. But nothing could ever prepare me for what happened on Tarotian. It was the size of an imperator titan, but made of flesh and blood. We thought it was a daemon. We readied ourselves for the end. It rampaged through our Baneblades and Leman Russes. Only non-stop fire from three Shadowsword tanks and an entire company of artillery brought it down. Then we heard that one had hit Cadia. It had annihilated whole legions on both sides. One hit Maccragge, home of the ultramarines. And then we realised this wasn't going to stop. All the races were hit by these kaiju, as the eldar called them. In the face of such evil, new alliances were formed. Alliances became friendships. We pooled our resources, the tau and the eldar and the humans. It wasn't enough. But salvation came. The Jaeger program was born out of ashes and blood." -Commissar Yarrick, on the early kaiju attacks.
Kaiju: named by the eldar after a mythical beast, the kaiju are a race of titanic creatures similar to tyranid bio-titans, but on a much larger scale. Each one appears to be unique, and they emerge from temporary dimensional portals known as breaches. Their destructive potential is greater than that of an imperator titan. They are the greatest threat that the galaxy has ever faced. However, the Jaeger program allows for some sort of effective defense.
Jaegers: invented by a collection of tau earth caste, Adeptus Mechanicus, and Eldar Bonesingers. Owing to their sheer destructive potential, the neural load formed by the interface necessary to link with a Jaeger is too much even for an astartes or Eldar. The only people capable of running solo combat are tau ethereals, Eldar farseers and space marine librarians. However, maybe once a generation, the universe offers up a handful of individuals able to run solo combat. The Jaegers are armed with weapons to put an imperator titan to shame. They are the first, last and only line of defense.
A few notable Jaegers:
Green Devil
Piloted by one of the few humans capable of solo combat, Aiken Sharratt, it is armed with massive lightning claws as well as two pulse submunition cannons. It is this fusion of tau and human tech that is stopping the enemy overpowering it instantly.
Shadow Titan
Another human Jaeger, Shadow Titan is a brutal fighting machine which forgoes all ranged weapons except for two racks of hellstrike missiles on its shoulders. Instead, it uses two fists that are basically chainfists and siege drills and thunder hammers all rolled into one to reduce kaiju to a bloody pulp. It is piloted by the ogryn Shronk, and an Astartes of the Imperial Fists, veteran-brother Gallius.
Isha's Fury
Isha's Fury, or Fury as it is usually called by its fellow pilots, is an Eldar Jaeger that uses raw, blinding speed to kill enemies. Piloted by two howling banshee aspect warriors named T'shanisha and Lin'oarta, it wields twin power swords and has brightlance arrays mounted on its chest.
Ethereal Fire
One of the few tau Jaegers specialising in close combat, Ethereal Fire is piloted by a kroot auxiliary known only as Paul, and a fire warrior called shas'montyr borkan'vral who everyone calls Monty. While it does have several ion cannons, the main power from its reactor goes to disruptor fields running along its bladed forearms. This allows it to mash any kaiju in close quarters, but leads to Monty and Paul being frowned upon by the "more evolved" tau. They have recently told fire caste command exactly where they can shove their heavy ranged weapons.
"Green Devil and Terminatus Extremis to the main hangar. C'mon, up and at 'em!" Aiken lurched up out of bed, banged his head on the ceiling, and made a short but eventful journey down to the floor from the top bunk. An Eldar aspect warrior who had just been pulling herself out of bed walked out of her bed and looked down at him. "Hey Shani," he said weakly. She replied with a look of sympathy, and yelled out. "Lin, Jaeger duty!" "Actually, it's a two-Jaeger drop and they've already picked Termin Ex." "Ah, dammit. I need to kill something." He grinned. "Sorry. Maybe it'll kill us both and give you guys a shot" "Well, you have to hope." He laughed. "Well, time to suit up." There were three Jaegers currently stationed on Typhon, two human and one Eldar. Terminatus Extremis, a Dark Angels Jaeger, and its two deathwing pilots were already in the hangar. Antrael and Enilius were already suited up. Aiken quickly jumped into his Jaeger, and powered it up. Two huge thunderhawk transporters clamped onto Green Devil's shoulders, and the same happened with Termin Ex. They flew.
The kaiju that the other races called Scutter emerged from the breach. It felt the clunk of landing feet, and growled. Its partner, Spear, growled as well.
Aiken stomped forward, pulse submunition cannons loaded and ready. Each one could behead a category one kaiju, but the enemy here was category four. Two of them. Termin was half a kilometre to his right. A kaiju signature flashed on his radar, a slight movement flickered on his optics, and he flew backwards. On the comm channel, he heard Enilius cursing in familiar, rich language. He activated his lighting claws, feeling the disruptor fields spark into being. As Scutter charged again, he let his claws swing and gouge four deep grooves in its side. His other hand curved round in a perfect left hook. As it rebounded off thick Kaiju hide, he activated his pulse submunition cannon with a thought and blew its head off. The headless corpse fell to the ground. His fight was won, but Termin Ex was in dire straits. The other Kaiju, Spear, was rushing it with no apparent intention of backing off. As he watched, the Kaiju seized the Jaeger with one hand while the other came round and grabbed the conn-pod. And squeezed. He yelled in fury. Activating the two melta torpedoes on his shoulders, he let both fly at the lizard-like thing. They both hit, blasting a hole through its stomach. It screeched in agony, but it still wasn't dead. Meaning to rectify this, he powered his pulse submunition cannons back up and let fly with the whole clip on each. Spear moved fast, but a few rounds clipped its right arm and flank. Its left arm clutched the stump of the now-absent limb. Out of ammo, he charged forward to finish it off. He sunk one set of claws into its chest as he grabbed its arm. Picking it up, he flipped it over his shoulder and broke its back. Then he activated the other set of claws and began carving deep furrows out of it to make sure it stayed dead. You could never be sure with Kaiju.
"We lost Terminatus Extremis yesterday, and Kurnous Spectre last week. We need more Jaegers." "There are two rookie crews just out of training, Shadow Titan and Ethereal Fire. Virtually no experience, but they show promise." "Okay. When do they arrive?"
The two Jaeger transports swooped down out of the sky. Out of the tau one's underbelly came the standard Cyclops design of a tau Jaeger. However, it seemed to lack the massive railgun batteries and ion accelerators of the standard tau Jaeger. Instead, Aiken saw the characteristic shape of a disruptor field generator. Out of the other craft came a Jaeger that was distinctly human. It seemed standard enough, with fists that could take a hive city to pieces. Commander Aramas spoke. "The new Jaegers. The tau one is Ethereal Fire, the only brawler with a tau pilot. The human one is Shadow Titan, and they're the new Jaegers I asked for." Shani spoke up from his left. "Nice." Then, alarms rang out through the base. "Two kaiju signatures detected, names Hammer and Colossus. Ready the Jaegers." Lin and Shani gave each other predatory grins.
The two Jaegers landed, the impact jarring the pilots. Fury took point, her swords crackling with power. Devil armed his cannons. The two kaiju read as three kilometres away, two, one and a half...he triggered his melta torpedoes and blew one into the middle of next week.