SALVATION

The 2204 strand. The human race has sent slower-than-light starships out to several stars, and begun terraforming their exoplanets. A portal system enables instantaneous transport between paired portals, so that once a starship has travelled to a new star at 0.8 lightspeed carrying a portal, travel to that star then becomes instantaneous.

In 2150 a huge alien sub-light arkship called Salvation of Life arrived in the sol system. It carries the Kax, who seem benign and claim their species is travelling in these ships to “the end of time”, where they believe their god awaits. They are hiding the fact they are fanatics who will stop at nothing to forward their cause, and take other species to their god for judgment.
Not all people believe the Kax are as peaceful as they claim. However, the Kax trade their advanced biotechnology with humans so they can build more arkships, which is advantageous to both species.
In 2204, a human starship entering the Delta Eridani system, the furthest humans have reached, discovers a crashed alien spaceship carrying humans held in suspension which has been there for decades, origin unknown. As faster-than-light travel is impossible, it is surely impossible for humans to have travelled this far out...
A team of five specialists is sent to investigate, one of whom is a spy. As they travel to the mysterious ship, the five take turns to tell their story. Each story explains how human society develops from today to this world of 2204, and gives possible clues as to who the spy is. Eventually, the spy is exposed as a Kax.
The Kax are a deeply religious race and a central tenet of their religion is that no lifeform should migrate beyond its home planet to contaminate other star systems. That humans are spreading across multiple star systems is a sacrilege to the Kax, who see themselves as guardians of the stars.

The AD 50,000 strand focuses on Delian, an Über human growing up on Juloss, a planet 20,000 light years from Earth: bigger, faster and tougher than normal humans. The Übers are divided into soldiers and smarts. Delian and his friends are brought up on the edge of a deserted city, they are the only people left on the planet.
As Delian grows up, he is put through subtle, then not-so-subtle training to turn him into an aggressive soldier. His body is also enhanced with the finest weaponry 10,000 years of research can build.
This story ends with Delian and his friends leaving Juloss in a fleet of huge warships, heading out into the galaxy in search of ‘the enemy’.