The Travelers are a fictional race created by Chaosium in 1994 for the Call of Cthulhu RPG, which was based on Michael Shea's The Autopsy.
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 enjoys the pain and horror their host experiences, as the trapped conscious is taunted and tortured.
A traveler's life cycle goes through for states, of which only the earliest stage, the larval form is mobile. It's adult form is a brain-like entity which controls a network of whip-like filaments. Which it uses to control the the host. They are also used as weapons by projecting from an orifice a paralyzing tendril and another one that extend's to the victim's hear to feed on its blood. The filaments can also be used to animate the dead by awakening the brain's memories.