Takes place sometime around 'Metalhead Rewired'.

After the escape and massacre caused by their second-favorite experiment, the Kraang were significantly more careful about the substance known as mutagen and the uses it was put to. It was not, they concluded after an investigation of the incident, a good idea to conduct their experiments without first making sure that the subject's mind was either broken or erased completely. They also agreed that observation was as useful as direct experimentation; seeing the subjects in their environments, how they interacted with the dominant species of the planet and with each other, was as vital as information as anything. And after the incident with their experiment, they decided to keep a much closer eye on their mutagen; their second-favorite experiment had turned out to be an terrifying threat, mostly due to their interference with its physiology and brain function and the incredible grudge it held against them for it. Within the past fifteen years, the investigation found, more than four canisters had been missing or broken on the planet Earth. Within the last few years, owing to careless handling in their partnership with various human operations, many more were misplaced.

The Kraang did not lose track of these canisters – recently all mutagen containers were equipped with a tracking device – but watched carefully as various humans and animals on the planet were very interestingly mutated. They kept careful tabs and files on every subject, studying biology, physical strengths and weaknesses, and mental capacities, observing from afar what exactly their mutagen could do in this strange, unpredictable dimension.

And the results were promising.

Many of the mutations were haphazard, inelegant – a gruesome mashing-up of parts and traits from the creatures combined by the mutagen: the creatures known as Squirrelanoids and the snakehead mutant formerly known as Xever Montes, currently known as Fishface, to name a few. The Kraang were especially interested in the mutant formerly known as Christopher Bradford, formerly known as Dogpound, currently known as Rahzar; his double mutation had had the Kraang scientists buzzing for weeks as they observed a complete lack of disintegrating mental capacities and a wonderfully, curiously stable mutation. After the human known as Shredder traded him for weapons, he became their third favorite experiment.

But although a few subjects didn't take very well with the creatures they were forcibly matched to, most of those affected had designs that were almost beautiful in the seamless melding of DNA:

The rat mutant formerly known as Hamato Yoshi, currently known as Splinter;

The turtle mutants known as Michelangelo, Donatello, Raphael, and Leonardo;

The tiger mutant known as Tigerclaw;

The gecko mutant known as Jason Mortello;

All and more exhibited completely stable mutations, with streamlined designs and sane, intelligent minds. The Kraang watched these more carefully, trying to discover what exactly caused these particular subjects to mutate so perfectly. The physical laws of Dimension X and Earth differed so greatly that the mutagen's effects were wildly unpredictable on Earth; what, then, caused these flawless mutations?

They hypothesized that certain blood types would cause stable or unstable mutations, based on the samples they had acquired from various blood banks around the planet. Unfortunately, they could never know for certain without directly experimenting on the subjects themselves.

A decision which, happily, coincided with their invasion plans of the planet Earth.

The mutants had established a heavy network of connections and communications, so the Kraang had to work quickly and quietly to acquire their subjects without alerting the rest. Those without powerful connections were taken first:

The spider mutant formerly known as Vic Shwartz, currently known as Spiderbytez;

The pigeon mutant known as Pigeon Pete, another escapee of theirs;

The chimpanzee mutant known as Tyler Rockwell, created by one of their agents on Earth.

After they allied themselves with the criminal organization known as the Foot Clan, they had significantly easier and faster access to mutants. The Foot was adept at capturing mutants and gave them to the Kraang in exchange for advanced weaponry, or what they thought was advanced weaponry; human technology was so simple in comparison that the Shredder was happy with mere plasma cannons. Their partnership even led to the eventual capture of the mutant turtle known as Michelangelo, thereby destroying one of the many obstacles in the way of Kraang Prime's plans.

As their plans progressed, the Kraang acquired more powerful mutants: the tortoise mutant known as Slash; the incredible garbage mutant formerly known as Henry Wright, currently known as Muckman. His psychic abilities were almost exactly what the Kraang were looking for, and his mutation was unique among the others, having drawn material from several different organic and inorganic substances. The cockroach mutant with bio-mechanical limbs paled in comparison.

But none of their captured mutants were nearly as important as their favorite experiment, the experiment they had cultivated through tens of dozens of Earth years, their pillar of perfectly-molded DNA and finely-tuned mental abilities that would allow them to develop a strain of mutagen stable on Earth and control those affected by it. The capture of their favorite experiment was surprisingly difficult; once she caught on to the fact that she was being hunted, she was adept at hiding and evading them – her developing abilities, attuned as they were to both the Kraang and the universe she resided in, no doubt aided her, but eventually the Kraang's human allies delivered her to their ship.

And their final plans could begin.

She was their singular specimen, their only chance – and they could not waste it by simply draining all her powers and disposing of her. They discovered that she had developed a way to listen to the Hive Mind, and so were incredibly careful about what they said or even thought in her proximity. They implanted her with trackers and monitors just as they had the others, measuring synaptic responses to pain and other stimuli. They recorded her vitals and her physical responses, noting a slight accelerated healing rate but few other physical manifestations of her mutation. Quietly, unobtrusively, they monitored her mental abilities from afar.

Her ability to tune into the Hive Mind was disturbing, but not unprecedented; they had programmed that, and it simply manifested earlier than they had planned. She seemed to have a slight sense of emotion, and with a little tweaking possible telekinetic abilities, but the Kraang decided to hold off on that experiment until they knew for sure exactly how much damage she could cause. Once, in a careless underestimation of her abilities, they had attempted to drill into her head to directly examine her brain matter; she had become distressed and psychically destroyed both their drill and the Kraang controlling it. Fortunately she did not remember the incident, but the Kraang were significantly more cautious after that. Until they could figure out the full extent of her powers and harness them, she needed to be kept as calm and as unknowing of their true plans as possible.

The Kraang had everything worked out, in every detail of code and sequence; they had plans for every eventuality, every roadblock and mishap possible. They had drills for emergencies, plans of action for unruly test subjects, and backups for the backups of every system on their ship.

But for all their planning, they had a hubris that they did not realize was dangerous, and in this pride they did not stop to consider that it possibly was a bad idea to give untested powers to a teenage girl with a grudge, and then experiment on her. While they were concealing their intentions from her, she in turn was hiding her own plans.

Two months into the capture of April O'Neil, the Kraang entered the lab specially set up for her only to find her gone from her cell unit. Their monitoring equipment showed nothing and had obviously been tampered with; the tiny glitches and small anomalies noted within the past weeks suddenly came to light as O'Neils experiments, until she was able to mentally connect herself to the machines and sabotage them. The trackers they had installed into her only gave her location as somewhere around on their ship, and they searched every room, hallway, closet, even the ventilation system without a trace.

Kraang Prime was contacted just as the tracker suddenly moved, away from the ship at startling speed, and the Kraang were unable to prevent their favorite experiment from falling directly into the river they hovered over. They watched in increasing horror as her vitals monitor went insane, and then flat-lined. Their favorite experiment had drowned.

April O'Neil, as a rule, ran more towards anger than despair when things turned to shit. Her mother died? Anger. Her father never came home from the grocery store? Anger. Creepy guys in suits chased her around town? Anger. Creepy ninjas kidnapped her and gave to the guys in suits, who turned out to be aliens with their brains in their chests and wanted to experiment on her?

Damn, she was pissed.

It didn't really do much – apparently the Kraang, as they referred to themselves, were quite prepared to put up with an enraged teenager, but once April discovered that she could do stuff with her mind she made a plan to escape. It took a while; the various experiments that they put her through occupied her for a long time: physical exams of endurance and healing, surgical implantations, pain tests…all time- and- energy consuming, until April was left aching and exhausted, almost too tired and hurt to really get angry.

The Kraang were very careful around her, she learned, and as the weeks went by (she assumed. Time didn't really have a whole lot of meaning in the lab) she discovered that their thoughts were open to her. They had the same realation and closed their minds as best they could, but not before April got a glimpse into their plans. Something about using her powers to take over the planet, or whatever.

It marked the moment that she got really serious about escaping. She'd initially shied away from the powers the Kraang were forcing her to discover, but now she quietly began to use them, expanding them without the Kraang noticing.

She surreptitiously searched through their minds, but her range was limited to the Kraang working on her directly, and she found nothing. So she turned her attention to their machines. It took a while, especially since she had to be so careful, but eventually she was able to mentally tap into their computer system.

She learned that they had been watching her for a very, very long time.

She learned that she wasn't the only one that was being experimented on.

She learned that her birth had not been a happy result of two people falling in love, but the meticulous arrangement of two finely-tuned strains of DNA.

And most importantly, she learned that she could hide from them.

She started small: tiny lines of code suddenly ruined, little glitches that could be put down as accidents. The Kraang didn't notice. She tweaked and tuned her control until she could make the monitors do or show whatever she wanted. And so one night she faked sleep, messed with her trackers, and made the Kraang's monitoring equipment show her to be enjoying a peaceful rest as she broke the codes for her cell and climbed into the ventilation shafts.

They were a little smaller and more cramped than April had seen on tv, but wasn't this how everyone escaped creepy labs and evil lairs? April shuffled through shaft after shaft, the occasional vent her only light as she tried to move toward what she thought was the outside of whatever they were keeping her in. It was a lot bigger than it had looked on the computer

She caught sight of what was going on in the rest of the place through the vents above and below her, not stopping for anything, until she managed to sneak into a crawlspace beneath what she figured to be the very bottom floor.

She saw them then. The experiments. The mutants.

Their pain hit her like a roaring wave, mental screams of agony and helplessness driving into her mind like sledgehammers and knives, until she thought she would burst from the shared pain. She was overwhelmed – her powers lashed out in an attempt to lessen the distress and she distantly heard small explosions and the pig-like shrieking of Kraang, before something twisted beneath her and she dropped through the floor.

She was falling, falling, down down through fresh, cold air that hit her face like needles, and she could barely crack her eyes open to see the river rushing toward her before she fell into its waters.

Two years have passed. The boys are all seventeen, April eighteen. Most of the events of the show have happened, though under different circumstances and with different timelines since they have not met April yet.

In this AU Snake was never mutated, because the kidnapping of April never happened. The boys just enjoyed a quiet first time above ground, and returned home without incident. Leonardo was chosen as leader of the team some time later, when they began to have conflict with the Foot and, through their partnership with Shredder, the Kraang.

The quote used for the title is "I find that what your people need is not so much imaginative art but that which hallows the vessels of everyday use." By Oscar Wilde. It's actually from a wabi sabi book I have, but I like the idea of appreciating things that are useful and but necessarily beautiful. This applies to people as well.