Disclaimer: Do not own Underworld, its sequel, or any and all properties associated with it. It belongs to some old guys whose name I can't recall at the moment. The idea, however, is mine. I've always felt slightly sorry for the Twins. Um. Spoilers for Evolution?

Hades

They can remember when they were once one, which makes their present situation all the more intolerable.

They aren't distinct entities, as such. 'Fragments', would be a better way to describe them. Remnants of personalities that were strong enough to challenge the sky itself, to split the world into inverse hemispheres of light and darkness. Half a millennia and more has passed since they were whole, but they still linger.

Linger where? In the blood? The bite? Perhaps. Whatever their source, they yet remain, after all else has fled. Splinters of their original selves, passed down through the generations from one hapless host to the next. They are quiet, for the most part.

Or rather, they would be quiet, if they had their way.

When it began, in the unnamed Event that forced flesh and bone to melt and merge against all lawful wishes of nature, they were cast apart. They had been one, once – each remembers that in a knowledge that goes beyond conscious thought. Where one once resided, two remained.

They never recovered from it.

Each sought the other with all the strength their heritage and will had granted them. With all the power of their birthright, they fought to be rejoined once more – they could remember what it had been like to be one, to be more, and they could not bear the knowledge.

It's more than possible they were driven a bit mad by it. As a matter of fact, it's practically a guarantee.

They linger in the bloodlines they have spawned, creatures that are part of them and yet separate individuals. Linked by the bands that tie kin to kind, each searching desperately for that single presence that once completed them. Over time, desperation fades to frustration. Frustration turns to rage, and they express themselves in the only manner left to them, inciting their hosts to hatred and madness.

They cannot ever be one again. They know that, and it drives their maddened wrath to new levels as they drive their childer to war against each other. Flesh is split, blood is spilt, and they can only find a final unification in the carnage they inspire.

The dead, after all, are equal.

If they cannot be one, the world will feel their plight. Better to fall into nothingness then to feel its presence throbbing within them. And so they rage and howl and scream, fluttering insubstantial wings and baring their throats to the merciless grasp of the moon.

OOO

It is the Darkness, and not the night, that sees their meeting once more within the shell of the last of their mortal kin.

The Wolf had prowled throughout his veins, testing the boundaries of the new host it had been born into, when the dark whirlpool had formed beneath it. It had growled, fanged bared, but could do nothing against the silver that the sweet moon had sent against its dwelling place. The one, and only, blessing that the orb had ever gifted it – the solace which lay in the ending of all things.

Yet even as the tempest grew into the bleak harbinger that was Death itself, the beast's head snapped up and it whined, puzzled. Something – something was-

The Bat had arrived on ivory wings, slicing into the sky that was its new home with a scream of possession directed at the core of life itself. It paused, surveying its new home with haughty dismissal before its head swiveled around -

And, for the first time in centuries, the brothers beheld each other.

A single moment of shocked recognition. Then they flung themselves at each other, clinging together in the midst of the maelstrom that roared around them. For a moment only they merely held on to one another, feeling frayed edges twist and heal, feeling the very boundaries of their essences twist and merge. Wounds long endured finally, finally fell silent. One. They were one. After centuries, the marvel had occurred, the miracle they had long since given up hope of ever occuring.

It was a blessing they had never expected to feel for their rest of the eternity that made up their existence.

A moment only they reveled in their simple existence, in the feeling of the other. Then their own matched roars of defiance challenged the growing storm as they clutched even tighter to the other and bent their power to their will.

After so many years, they were once more reunited, and there was no power in heaven or hell that they would ever allow to separate them again. The Two were One once more, and death could not have them.

The black whirlpool shuddered, shattered, under the force of their might as they made their host anew, as they mingled into his very essence. Separate, yet still a part of him, the black of the Darkness which had reunited them growing in his eyes.

Claws burst from his fingers – the Wolf's benediction. The night soaked into his very skin – the Bat's gift. And more, so much more that they lavished freely on the one whom had brought them together once more – their favored childe.

For the first time in centuries, the changes they inspired were a blessing, and not a curse to be reviled. The birth of something new to this world, something that would be free, rather than the recruitment of yet another soldier to the eternal war.

They settled back into their proper place, each still clutching at the other as if never to let go.

The Wolf nuzzled sleepily at the Bat, resting a furry head against cool skin. I missed you.

The Bat ducked its head, wrapping leathery wings about its otherself. So did I.