Note: I forgot I had this. Dug it up out of my blog while I was cleaning things. Enjoy!
They had all gone their own ways long ago. As they had always known he would, Donatello transcended them all. He would have stayed for them, had they asked, but they loved him too much to limit him. Michelangelo's seemingly never-ending well of talent naturally bore him off, as well, to try his hand at, oh, pretty much everything—a dizzying array of experience to finally realize his potential, make him more than the baby of the family. And after much flailing and explosion, Raphael at last found the cause to commit his boundless passion to. His family had always known his destiny, working tirelessly all those years in order that he choose a cause worthy of him.
Then there was Leonardo. None of them—even he—had much considered his future. After all, he'd been so very much there, fulfilling himself so very obviously before their eyes. In the end, he simply vanished. Oh, they heard from him, now and again, never from the same place twice, never in any discernible pattern or schedule. He didn't try to be elusive; more like he'd simply started wandering and never stopped.
Nevertheless, in a family like theirs, some things are inevitable. Too many ghosts in their pasts refused to lay at rest, and no question that some unfinished business would rear its head at last to call them back together again. So it was that these four found themselves standing together, so many years later, marveling at the changes they saw in one another, etched over the familiar things that would never change.
They'd thought themselves adults when they'd closed the Lair's door that final time. Now, hammered in the forges of life, they knew the meaning of the word. They saw Raph's fires banked and focused, a cutting laser to his old conflagrations. Donatello, once the most isolate brother, now the world-wise one, steeped in the knowledge and experiences of a thousand worlds and dimensions. Michelangelo—perhaps the most dramatic change—was sunny and open-hearted as ever. Yet they looked into his face to see a comfortable maturity lurking beneath the twinkle in his eyes. It suited him well. Almost a shame, perhaps; in another world, he might've made a wonderful father.
And again: there was Leonardo. Where the others had grown and changed, he had simply concentrated. One might say that he was more than ever himself: as they had always known him, only, always, Leonardo. Though they had always relied on his calm, his serenity now gave the lie to his old veneer. These days, silence followed him into a room like an old companion. So quiet was he that they sometimes caught themselves forgetting him, until after hours of contemplation he might stir to interject into their conversations, having found something he thought worth their attention. He slipped through their senses like a ghost, unobtrusive near the point of non-existence, a whispering presence that made no demand on their attention. He simply sat in stillness and waited, like an observer on a scene he no longer held claim to.
In some ways, he reminded them of Splinter: in the way he might watch them for hours, for example, simply drinking in their presence; in the way he seemed rooted to his surroundings as though part of them; and in the way he seemed to fill a room simply by being in it. Yet, the truth was he was not really much like Splinter at all. Their father's nature had warmed and enfolded, made all right with the world for four dispossessed young turtles. Leo's cool poise doused even Raphael's temper, as though drawing the heat from everything around him, but in the smaller scheme of things (and really, what else mattered?) it did little to reassure.
Raphael, who had never claimed a tendency toward philosophy, thought that Leo was more familiar to him, somehow, than he had ever been. Leo had always held a special affinity for his weapons beyond what his brothers shared with theirs. Now, refined in himself, he stood tempered to a clean purity, as hard and fine as the blades he wielded. Donatello, always up for a riddle, considered the sweet chill of a mountain lake, or the blue-white of a glacier's ice: numb and beautiful, except for the smile he sometimes caught in Leo's eyes. More himself than ever, Michaelangelo said, having always known his brothers better than they gave him credit for. Thus, Mike wasn't too surprised when, as usual, Leo's actions told them more than he ever said in words.
They were all warriors, in addition to anything else they chose to be. Each of them had killed, and lost, and been saved by their skills in the past. They knew Death well enough. With his death, Splinter had sealed them all forever to the art. It became a part of him that they could keep and nurture, so that not even Donnie or Michelangelo, with all their distractions, could bear to let go of their training. But Leonardo, who never much cared for such things as dreams and passions, had only ever lived for two things. When his brothers left him, he was left with one.
So when he finally came to rest, falling still like a clockwork dancer winding down, they understood that he had surpassed them in this as they had surpassed him in so much else in life. They had each embraced some aspect of themselves, and he had chosen Death as his favorite. It occurred to Raphael, in fact, that Leo had done this long ago. They'd simply never bothered to name it before. He wondered now how Master Splinter must have felt, since surely he had known.