The Caleuche was a name attached to Traveling Fearlessly's void warren by crew members of the Flotilla. Having its roots in a ghost story about a ship that was capable of vanishing into the night, few would ever know the alien vessel existed.
Sometime after the launch of humanity's first manned interstellar colonization effort a grub named Traveling Fearlessly was drawn to the five antimatter flares of the fleet, maneuvering his void warren to trail them. The vessel was capable of remolding itself -- or at least its outer hull -- into an approximation of the human-built colony ships -- a camouflage tactic ten million years of grub usage had determined was generally effective, though when it was noticed the average response was highly aggressive.
Unfortunately, one of the five ships, the Islamabad, was destroyed in a sudden and unexpected antimatter explosion. The blast wave crippled the void warren, reducing its force-projection capability to the formation of only a partial armouring skein -- though its inertia-suppression technology and internal manipulation of gravity appeared to be unaffected.
Still drifting behind the Flotilla, the virtually helpless void warren was eventually detected and boarded by a crewman of the Brazilia: Lago. Arriving secretly by shuttle, piloted by fellow crewman Oliveira, Lago entered the alien craft and was eventually "eaten" by Traveling Fearlessly, after panicking and killing several of its helper grubs. In actuality his memories were absorbed by the grubs and his biological components appropriated for other uses. After the traumatizing killing of his friend, Oliveira killed himself.
Years later Sky Haussmann, along with fellow crewman Gomez and Norquinco, also located the famed "ghost ship". After discovering the fate of the two Brazilia crewman and the presence of two more shuttles on the way toward his prize, Sky knew he could not keep it a secret for long, and decided to destroy it -- and kill Traveling Fearlessly -- rather than risk its technology falling into the hands of other Flotilla ships.
After forcing Traveling Fearlessly to use its vessel's force-projection technology to create a solid barrier in the path the two approaching shuttles, destroying them, he retreated to his shuttle and detonated a harbourmaker nuke inside the void warren.
- Traveling Fearlessly seemed affronted by Sky's assumption that his void warren was equipped with weapons, hinting at the possibility that the grubs simply did not utilize conventional ship-board armaments as humans did; relaying totally on their defensive "armouring skein".