A familiar was a sub-sentient timeship.
Aware of the approaching War, the Homeworld had tried to create timeships which could communicated directly with their operators. The first effort, the 101-project, was a massive failure. With Compassion still unwilling to help, they decided to attempt a more gradual approach, breeding timeships with animal-level intelligence.
In this they were successful, making ten. They did have a need to bond, so they escaped and each one swallowed a technician before disappearing, never to be seen again.
The familiars were not seen as threats, and their development led to the priming protocols which were used for the subsequent 103-forms. (PROSE: The Book of the War)