The Bezen Symiotes Aphra described were more like a species of psionic parasite native to the Star Wars Universe. Listed as an extremely dangerous species under the Galactic Covenant, they were strictly forbidden from private study or weaponization. Even the Sith Lords were wary of them and wanted them wiped out.
No one knew where they came from. All anyone knew was that they were ancient, scattered across the Milky Way Galaxy, and that an ancient Beicen might be sleeping in a cave or ruin on any given planet.
They chose species they liked as hosts, such as humans, whose bodies were simple and whose Mental Power was weak.
While dormant, the creatures looked a little like miniature Aliens. Once awake, though, they took on a psionic form resembling black smoke or mist and lodged themselves in their hosts' minds. Together they formed a Gestalt Network led by the Brood Queen, driving their hosts around like tanks.
The hosts retained their own awareness and thoughts. They simply could not control their bodies.
But there was a problem. Symbiotes in the Marvel Universe made both themselves and their hosts stronger. Bezen Symbiotes made both sides weaker.
Before finding a host, they could enter an intangible psionic state. In that form, they were nearly invincible; even the Force could not destroy them.
Without hosts, however, their mobility was severely limited. They had no way to spread through space.
Once bonded with people, they could pilot starships and travel farther. But at that point, killing their flesh-and-blood hosts would kill the Bezen Symbiotes as well.
This was symbiosis in the truest sense. It gave them an enormous weakness they had never had before.
Aside from granting their hosts eternal life, they offered no enhancements whatsoever. They could not even use the Force after