Imagine a giant underwater bio-factory that manufactures these things - and instils them with the instinct to explore and then return memories and experiences to the 'mother'.
Imagine that said bio-factories are among the earliest living things the universe ever produced, and that some of their 'offspring' eventually developped tool use and intelligence, made their way into space, harnessed the resources of their system, and spread by STL means throughout the galaxy. Always with the instinct to explore and return home with memories and experiences.
Imagine that wherever these 'offspring' went they seeded with genetic material that would spur whole worlds into becoming oases of life, possibly intelligence. Several 'daughter' races discovered the extra dimensional nature of reality and opened up the realm of psionics.
Eventually, far into the future, a genius mutant would be born to a 'daughter' race who would find a way to mechanically access higher dimensions and make jump drive possible.
When the Abyssals eventually learned of this breakthrough they became very interested in that part of the galaxy. Of course it would take hundreds of thousands of years to send 'agents' to learn the secrets of jump drive and return; then again there is always the instinct to return and share memory and experiences, all it needs is to trigger it...
