Some of them will have their own ships. I think they will probably start out as purely defensive, sort of "guards" for "treasure", but with more development time, eventually they should be able to be more active -- pirates should raid nearby systems, Gardeners should try to spread their ecology, etc.
An Eldritch abomination is really any mysterious, obscure, ancient, and incomprehensible being. From what I can gather, the Esk are one such monstrous race of eldritch things that are impossibly evil and ancient.
If you're familiar with the works of H.P. Lovecraft, he wrote about many eldritch abominations, such as the Great Old Ones and their leader Cthulhu, the Elder Things, Father Dagon and Mother Hydra, Nyarlathotep, and more.
Hm, I see. I know a little bit about Lovecraft and have heard of Cthulhu but not too much, but never heard about an Eldritch. Thanks for the explanation.
I actually visited the game's webpage, and it would seem that the game actually draws some inspiration from Lovecraft, which would probably explain the name. This discussion certainly brought some new things to light.