Galactic North is a collection of science fiction short stories by British author Alastair Reynolds, published by Gollancz in 2006.
Reynolds states in the afterword to the collection that the stories are set in rough chronological order, with "Great Wall of Mars" occurring around AD 2200, whilst Galactic North extends to AD 40 000 In this short story, we meet Nevil Clavain, one of the protagonists of the Revelation Space cycle; Galiana, the founder of the Conjoiner faction; and Sandra Voi, an important person in the Demarchist faction.
The story begins on Deimos, where Nevil Clavain, a high-ranking officer in the Coalition for Neural Purity is preparing to go down to the surface of Mars.
Eventually, Clavain and Voi depart and fly down towards the Great Wall of Mars, which turns out to be a massive construction that completely envelops part of the planet's surface (enough to cover a city) and the atmosphere above it.
Clavain also meets Felka, a girl who was part of an experiment to further improve human intelligence by altering the brain in the womb.
It failed miserably and Felka seems completely uninterested in anything except the mysterious game she is playing – she keeps waving her hands around in a pattern.
However, the attack has damaged it so badly even she cannot keep it intact for long and soon the wall will collapse, causing the atmospheric pressure inside to be released and tear the base apart.
The Conjoiners have escaped upon their starship, named the Sandra Voi, to an ice planet called Diadem (which orbits the star Ross 248).
It is home to an American colony, seeded decades ago by automated robots containing human DNA, but it appears deserted.
They meet in the city and Cholok reveals that she has a piece of "Hyperdiamond", a carbon compound that is extremely strong – individual molecules can be hundreds of metres in diameter.
He meets a group of Denizens who kill the Demarchist agents and inform him that Cholok created them, but the Demarchy turned them away and imprisoned them in their cave.
Weather tells Inigo that the Conjoiners considered the act a kindness, but failed to realise the effect it would have on loved ones of the people they transformed.
He is awoken from reefersleep (a form of cryogenic suspension) by Katia, a beta-level simulation of his real wife, who he had left behind on Yellowstone after the Melding Plague.
Jax reveals to Dexia the ship's intentions: it was unable to reconcile itself with the fact that the people it was healing would be returned to the war.
It was about to kill Jax, but decided to turn him into a war monument to stop the fighting, and has spent the intervening period working on its masterpiece.
This story starts in the year 2303, when Captain Irravel Veda of the lighthugger Hirondelle, her second-in-command Markarian, and some fraction of their Ultranaut crew are ambushed by pirates while engaged in an unexpected repair stopover in a cloud of rocks and cometary matter in the charted but uninhabited star system Luyten 726-8.
She briefly considers activating the "Greenfly" terraforming Von Neumann machines being transported on board, which she believes would easily be able to swarm and dismantle the pirate vessel and probably aid in repair as well.
She discovers that almost all of the colonists have been taken, while the handful that were left behind have been cut to pieces in order to acquire their tissues and implants; the valuable Greenfly machines they were transporting have also been stolen by Seven.
Irravel does not trust her, but Mirsky demonstrates her independence by violently removing the implanted mind-control device that Run Seven had been using to recruit and maintain his crew.
They awaken Remontoire, one of the Conjoiner passengers on the Hirondelle and use his expertise to effect repairs and track down the pirates as they flee the system.
In the midst of a tense standoff, however, Irravel's conditioning causes her to strike a deal with Seven, offering him Remontoire and the rest of her crew in exchange for the colonists Seven had abducted.
Her body is saved and her brain is scanned into in the ship's computer, brought back as an alpha-level simulation whilst the Hirondelle is orbiting its final destination of Yellowstone in 2415, before the advent of the Melding Plague which would later destroy the nanocybernetic infrastructure making this possible.
Still under the influence of her Ultranaut conditioning, Irravel gives chase, interested in exacting revenge, rescuing the colonists, and learning why Markarian gave up the codes to their security.
By 2931 she has followed him to a refuge among the "Nestbuilder" race, from whom she attempts to purchase advanced weapons technology in order to have the advantage against the Hideyoshi during the next encounter.
In their last conversation, they discuss the Greenfly, which they observe by now has begun spreading to other systems, destroying the intelligent societies it was designed to provide for.
She also discovers that herself, Markarian, Mirsky, and Seven, their confrontation having unleashed the Greenfly upon the galaxy, have receded into the mists of prehistory and become mythologised as primordial figures.
During the feast later that evening, she tries to tell them that she truly is the same person depicted in the Islanders' play, but they disbelieve her, as many Irravels make such insistences with no particular claim to legitimacy.
They explore the Hideyoshi and find it abandoned, learning that Markarian has been physically absorbed by the medichines sustaining him in his old age, and exists now only as a collection of software servers which simulate his behaviour.
They collect the remaining colonists (whom Markarian has stored as alpha-level neural scans plus complete genetic archives) and prepare to leave the galaxy to re-establish a new civilisation elsewhere, fleeing just ahead of an immense nebular swarm of Greenfly machines which had homed in on Hope as it fled the galactic plane.
The novel Absolution Gap contains a reference to entities in a parallel universe (or at least claiming to be from one) facing attack from an agent very similar to the Greenfly.