But he could speculate how it had spread. Photino creatures like birds — photino birds — had fluttered out through the baryon stars as if they did not exist, colonizing shadow world after shadow world. Perhaps, Paul supposed, vast flocks had plied between the hearts of stars, with the humans and other baryonic races all unaware.

Aeons had passed with the two grand families of life, dark and light, oblivious of each other…

Then something had happened.

Again Paul could only guess. Probably a supernova had ripped apart a baryon star, laying waste to its host shadow world in the process. Paul imagined the horror of the photino civilization as the irrelevant froth of baryons through which they moved turned into a source of deadly danger, perhaps threatening the ultimate survival of their civilization.

Many courses of action must have been considered, including — Paul speculated with a kind of shudder — the total annihilation of the baryonic content of the Universe. But without baryon stars and their tiny gravity wells new shadow worlds could not form; therefore without the baryons there could be no replacement for the photino worlds as they grew stale and died: and so, in the end, the dark civilization itself would falter and fail.

So the baryons had to stay. The photino birds needed the stars.

But they didn’t need the damn things exploding all over the place. And the Universe was full of these vast, gaudy stars, burning off energy and forever quivering on the brink of catastrophic explosions. Such extrovert monsters were simply unnecessary; all the dark races required from a star was a reasonably stable gravity well. The remnants of large stars — white dwarfs and neutron stars — were quite satisfactory, and so were immature stars: the brown dwarfs and Jovian gas planets which were warm but not quite large enough for fusion to be initiated.

Cold, dull, and immensely stable. That was how a star should be.

So the photino birds set out to transform the Universe.

The photino birds set up two great programs. The first had been to shape the evolution of new stars. Paul imagined invisible flocks cruising through the vast gas clouds which served as the breeding grounds for new stars; the photino birds had used huge masses to skim layers off protostars and so condemn them to become brown dwarfs, little grander than Jupiter.

The second program had been to rationalize existing stars.

If the things were going to explode or swell up like balloons, the photino birds had reasoned, then they would prefer to accelerate the process and get it out of the way. Then the photino civilization could grow without limit or threat, basking in the long, stately twilight of the Universe.

So the photino birds had settled into the hearts of stars. They infested the core of humanity’s original Sun.

For millions of years, unknown to humanity, the photino birds had fed off the Sun’s hydrogen-fusing core. Each sip of energy, by each of the photino birds, had lowered the temperature of the core, minutely.

In time, after billions of interactions, the core temperature dropped so far that hydrogen fusion was no longer possible. The core had become a ball of helium, dead, contracting. Meanwhile, a shell of fusing hydrogen burned its way out of the Sun, dropping a rain of helium ash onto the core…

Five billion years early, the Sun left the Main Sequence, and ballooned into a red giant.

With such cool calculation, such oceanic persistence, the photino birds made the stars old.

Soon the first supernovae began. They spread like a plague from the photino birds’ center of operation.

And the Xeelee became troubled.

By this time, Paul speculated, the Xeelee were already lords of the baryonic Universe. They had initiated many of their vast cosmic engineering projects, and a host of lesser races had begun to dog their gigantic footsteps.

The Xeelee focused attention on the photino birds’ activities, and rapidly came to understand the nature of the threat they faced. In peril was not just the future of the Xeelee themselves, but of all baryonic life.

Perhaps they had tried to communicate with the birds, Paul speculated; perhaps they even succeeded. But the conflict with the photino birds was so fundamental that communication was meaningless. This was a dispute not between individuals, worlds, even species; it was a struggle for survival between two inimical life modes trapped in a single Universe.

It was a struggle the Xeelee could not afford to lose. They abandoned their projects and mobilized.

The final War must have started slowly. Paul imagined Xeelee nightfighters descending on stars known to harbor key photino bird flocks, cherry-red starbreaker beams shining like swords. And there would be reciprocal action by the photino birds; their unimaginable weapons would slide all but unobserved past the best defenses of the Xeelee.

And the Xeelee must, about the same time, have initiated the construction of the great causal loop controlled by the antiXeelee with its seed pods. At last Paul understood the antiXeelee’s purpose: the Xeelee had, with awesome determination, decided to modify their own evolutionary history in order to equip themselves for the battle with the photino birds. Paul pictured a branching of the Universe as the antiXeelee changed the past. The Xeelee, modified and pre-warned, had time in this new history to prepare for the coming conflict, including the construction of the mighty artifact called Bolder’s Ring — an escape route in case, despite all their preparation, the War were lost.

And all the time humans and other races, oblivious to the great purpose of the Xeelee, had scrambled for abandoned Xeelee toys. Eventually humans had even had the audacity to attack the Xeelee themselves, unaware that the Xeelee were waging a total War against a common enemy far more deadly than the Qax, or the Squeem, or any of man’s ancient foes.

The Xeelee wars had been a ghastly, epochal error of mankind. Humans believed they must challenge the Xeelee: overthrow them, become petty kings of the baryonic cosmos.

This absurd rivalry led, in the end, to the virtual destruction of the human species. And — worse, Paul reflected — it blinded humanity to the true nature of the Xeelee, and their goals: and to the threat of the dark matter realm.

There was a fundamental conflict in the Universe, between the dark and light forms of matter — a conflict which had, at last, driven the stars to their extinction. Differences among baryonic species — the Xeelee and humanity, for instance — are as nothing compared to that great schism.

And, even as the wars continued, still the cancer of aging, swelling and exploding stars had spread. The growth of the disrupted regions must have been little short of exponential.

At last the Xeelee realized that — despite the deployment of the resources of a Universe, despite the manipulation of their own history — this was a War they could not win.

It remained only to close the antiXeelee’s causal loop, to complete the Ring, and to flee the Universe they had lost.

But already the birds were gathering around the Ring, intent on its destruction.

Paul brooded on what he had learned, on the desolation of the baryonic Universe which lay around him. Though the Ring survived still, the Xeelee had gone, evacuated.

Baryonic life was scattered, smashed, its resources wasted — largely by humanity — on absurd, failed assaults against the Xeelee.

Paul was alone.

At first Paul described to himself the places he visited, the relics he found, in human terms; but as time passed and his confidence grew he removed this barrier of words. He allowed his consciousness to soften further, to dilute the narrow human perception to which he had clung.