Now, as a far more formidable foe gathered, the Ascendents turned to Saturn once more. Earth itself was to be corralled with gravitation and brought out here, to circle on the rim of Saturn’s mighty gravity well, where it could be protected. And the war machines under those clouds, already powerful, were enhanced with the accumulated learning of a million years of interstellar war.

The purpose of the undying had been unswerving. But this project was not quite as under their obsessive control as they would have preferred. There was risk.

‘I don’t understand,’ Mela said. ‘What risk?’

The Curator waved a hand, and the air was filled with a high-speed chatter of automated signals. Symat thought he picked out questions and responses, handshaking, a kind of dialogue. The Curator said, ’The Guardians are very old. They have long since got used to making their own decisions. When a ship like this comes sliding into their space, they get very suspicious. Can’t you tell, from the way the drones are swarming around us? All that’s keeping us from being destroyed right now is our flitter’s responses to the Guardians’ continual interrogation.

‘And when the Ascendents decided to move Earth here - Lethe, a whole planet sliding across Sol system - one false word and the home of mankind might have been blown to bits by machines meant to protect it.’

Symat said, ‘We’ve been at war with the Xeelee for a million years. What can these Guardians have that’s so powerful it could make a difference now? And why hasn’t it been thrown into the war before?’

‘I think I can answer that.’ Mela’s eyes clouded, and there was a sheen about her face, a waxy unreality. She screwed up her forehead as she tried to integrate the information pouring into her head.

Long ago, as mankind advanced across a Galaxy, under a purposeful programme called the Assimilation, whole alien cultures were eradicated or subsumed, their technology and learning purloined. Most such treasures, as Symat had guessed, had been thrown into the vast war effort. But some had been secreted away by the patient undying. Insurance for the future, they thought of it.

One such was the technology called the Snowflake. It had been found in orbit around an ancient star in a globular cluster out in the Galaxy’s halo. It was a stunning artefact, a regular tetrahedron measuring over fourteen million kilometres along its edges. Humans gave it this name because like a snowflake the structure had a fractal architecture, with the tetrahedron motif repeated on all scales. And the Snowflake, it was discovered, was full of information: it was an iron-wisp web of data, a cacophony of bits endlessly dancing against the depredations of entropy.