Please understand that I am looking more for an "out of game" reason rather than an "in game" reason. That is, of course, assuming that there is one.
Just hazarding a guess here...
ISTR remember a sci-fi book which featured a seeming predator called "rugbird". I can remember chunks of the plot, but not the book's title.
The plot involves a "foreign legion" style military unit operated by the interstellar government. Men join this legion to literally forget. You sign up and get a memory scrub of sorts which erases what you no longer want to remember. The books hero wakes up after such a procedure and, instead of no longer knowing certain names, dates, and events, has "forgotten" nearly everything. Whatever he wanted to forget was also intertwined with most of everything else he knew.
The hero's lack of knowledge allows the author to "explain" all sorts of things regarding the books setting. For example, FTL is by teleportation. Ships look like quonset huts, have a "sending" and "receiving" tower on each end, and teleport themselves to themselves at FTL speeds. After joining the legion, the wholly ignorant hero thinks he's waiting in a hut, wonders what is taking so long, and tries to open the door only to be stopped by his shocked companions.
Anyway, the hero is pursued by two gold-skinned humanoids for most of the book. The humanoids are tireless, possess superhuman speed. superhuman damage resistance, and other fantastic attributes. At one point, the hero sees them effortlessly clinging to the outside of a spaceship in vacuum. Eventually, the humanoids capture the hero and begin to "feed" to a "rugbird". What happens next explains everything which came before.
The "rugbird" is described as a the size of a large mat or small carpet with thousands of small feeding tubes on it's underside like those of a starfish.
Apart from
Traveller, that book whose title I cannot remember is the only place I've come across the term "rugbird".
