Stargate: 10 Best Aliens In One Episode Only
8. Reetou
The Reetou were a peaceful race who existed just outside of human perception. This made them invisible to the unaided eye, yet also made them immune to most projectile weapons. They were not immune from all weapons though and were almost wiped out by the Goa'uld, simply for the potential threat that they represented.
The surviving Reetou split into two camps. There were those who were loyal to the Reetou Central Authority. These believed in fighting the Goa'uld themselves, in a unified force. However, the breakaway group of Reetou rebels believed in a war of attrition - targeting any potential host, leading to an attempted invasion of Earth.
With the aid of the Tok'ra, the SGC are able to overcome these rebels, though they are warned that the Reetou will never stop trying to destroy potential hosts. With that grim thought in mind, even though they hadn't been seen again, there was nothing to say that some of the 'missing in action' reports were due to Reetou, hiding out of sight.