Rat-Shrimp
The "Rat-Shrimp" is a hallucination suffered by multiple crewmembers of the PUV James Keeling.
Not everyone who hallucinates this creature sees the exact same thing, but the Rat-Shrimp visions have enough in common to be grouped together.
Excerpt
From SHAKEDOWN: Its knobby, pointed head—at least John assumed it was the head—was as wide as a man’s chest, with fist-sized, silvery bulbs on either side. Eyes? Probably eyes. The creature seemed to be made up of joined bits of shell, like a shrimp or an insect, but the shells were covered with mottled tan fur, glossy and short. The fur reminded John of rat hair. Thin, iridescent green growths jutted out from what might be a chin. Were the growths antenna? A fashion statement? Maybe a nasty infection? He didn’t know. Sigler, Scott. The Crypt: Shakedown: (A Military Sci-Fi Novel) (p. 157). Aethon Books. Kindle Edition.
From SHAKEDOWN: He looked at his platoon’s second in command, strapped to her bunk with zipstrips. Sitting on top of her was a rat-shrimp-thing, iridescent green mouth-bits puffing away on a meter-long, blue glass bong in the shape of a Rogalinski rifle. Big, silvery eyes stared at John. Tan-furred cheeks puffed—one, two, three perfect smoke rings, slowly expanding outward. Sigler, Scott. The Crypt: Shakedown: (A Military Sci-Fi Novel) (p. 301). Aethon Books. Kindle Edition.
From SHAKEDOWN: (Dardanos) Leeds nodded slowly. “There’s like a… boy-sized… thing standing on the slate. Big silver eyes. It’s… it’s smoking a hookah.” Sigler, Scott. The Crypt: Shakedown: (A Military Sci-Fi Novel) (p. 362). Aethon Books. Kindle Edition.
From VOIDSTRIKE: "It reminds me of a prawn. A furry prawn.” He held his hand out, chest-level, palm-down. “Maybe about this tall. I think it had three eyes… kind of satin-gray. Some stuff on its face, might have been eyes. Really wide head. And some stuff coming out of its chin.
Issac made a note, but Akagi sat up straighter.
“Green stuff,” he said to Brogan. “Like a stiff beard, kind of?” Akagi put his knuckles to his chin, waggled his fingers. “Or like… ferns or some shit?”
Language
Some have reported that the Rat-Shrimp make high-pitched noises that might be language of some kind. Some describe the sound a similar to a breathy flute.