Stargate: 10 Best Aliens In One Episode Only
4. Reol
The Reol, or as this individual is also known as, Tyler, appears in the fifth season episode The Fifth Man. They have the ability to secrete a chemical that allows them to implant suggestions in others' minds - this allows one of their race, Kaiael, to infiltrate SG-1. However, his intentions are protection, rather than anything malicious.
The Goa'uld have hunted this race to the point of extinction. This chemical is seen as too excellent a strategic advantage for them to pass up, much to the Reol's misfortune.
This particular individual, Tyler, becomes a part of the team - the point where he attempts to sacrifice himself to ensure SG-1's safe return to the SGC. However, chemicals aside, he had endeared himself so much to O'Neill that the team save him anyway, earning another friend in the galaxy.