The Travelers are a fictional species expanded upon by Chaosium in 1994 for the Call of Cthulhu roleplaying game, which were based on creatures which appeared in Michael Shea's 1980 short story "The Autopsy".
Background[]
Travelers are a spacefaring race whom travel across space using translucent ships the size of basketballs. When approaching a planet they use meteor showers as cover. If detected, the ship auto-destructs, creating an explosion large enough to take out a city block. The Travelers remain hidden until they can invade a suitable host. The alien parasites are a sadistic race which enjoy the pain and horror their host experiences, as the trapped consciousness is taunted and tortured.
A traveler's life cycle goes through four stages, of which only the earliest stage, the larval form, is mobile. Its adult form is a brain-like entity which controls a network of whip-like filaments which it uses to control the host. They are also used as weapons, projecting from an orifice a paralyzing tendril and another one that extends to the victim's ear to feed on its blood. The filaments can also be used to animate the dead.