|Out of universe information|
The Reol are a race of humanoid aliens, supposedly from the Milky Way. They are a peaceful race who were almost wiped out by the Goa'uld. They were forced to abandon their home world because of the Goa'uld.
The Reol have a unique natural defense; one of their bodily secretions is used to create false memories and illusions when it comes into contact with a living creature. Their appearance are very tall, lanky bipedal creatures with thick strands of hair and dark black eyes. Their heads appear almost skeletal in shape. The Reol have also decided not to embrace technology to the extent that no other species have. They were only encountered once by the Tau'ri when they met a member named Kaiael, who took the appearance as a fifth member of SG-1, Lt Tyler. (SG1: "The Fifth Man")
This secretion is the only advantage the Reol have, as they are peaceful creatures and are hardly able to defend themselves. This defense mechanism can make an individual believe that the Reol is not a threat, and will allow a Reol to incorporate him or herself into the culture of the infected species to avoid detection. It also has the ability to alter memories and to make the Reol appear as one of the target's own species, and is therefore the perfect camouflage. Though it is an advantage, it is also the reason they are nearly extinct, as the Goa'uld fervently wish to discover the secret behind the substance. There are only a handful of Reol left. However, a group has settled on a world unknown to the System Lords in the hope to rebuild their culture. With help from the Tau'ri, the Tok'ra have developed their own version of the Reol substance, which was used by Daniel Jackson to infiltrate a System Lord summit and later again by Cameron Mitchell to infiltrate the Lucian Alliance. (SG1: "Summit", "Last Stand", "Company of Thieves")