R: ra, reetou, ribbon device, rya'c...

[Vern]

Ra
Ra was the enemy Goa'uld in the Stargate Movie, where he ruled over the mining population of Abydos. Ra was a powerfull System Lord, and was responsible for finding Earth (the Tau'ri) and taking humans as hosts.
Ra was killed at the end of the movie when Colonel Jack O'Neill transported a bomb onboard his mothership.
Ra has many links to the other Goa'uld we see in Stargate SG-1. He was an enemy, and brother, to Apophis. He defeated Egeria, the Tok'ra queen found in the episode "Cure". Ra was also the husband of Hathor, and father of Heru-ur.

Ra was the sun god in ancient Egyptian Mythology. And was also known as Re, Atum-Ra, or Amun-Ra.
Ra was the almost universally-worshipped king of the gods and all-father of creation. A sun god, he was said to command the chariot that rode across the sky during the day. A king, he was the patron of the pharaoh. Ra is the most central god of the Egyptian pantheon.
Ra's position in the pantheon is unusual. He is the only god, apart from Osiris, who is definitely said to be not on the earth. Ra, it is said, is an aging god, still powerful, but too old to deal with his children any longer, so he has gone exclusively to the sky to watch over the world. Horus rules over the earth and the gods in his stead, demonstrating the divine right of kingship.


Reetou
No longer living on their homeworld, Reetalia, which was destroyed by the Goa'uld, the Reetou are able to render themselves invisible. A large rebel faction believes that by killing all potential hosts for the Goa'uld they gradually will eliminate the Goa'uld themselves. The Reetou first appeared in the episode "Show and Tell".


Ribbon Device


Rya'c

[Chey]

Replicators
Spider like robots, they are enemies of the Tauri, Asgard and Goa'uld. They can replicate and are unaffected by weapons such as Zat'Nik'Tel's.

[CaptainHaz]

Rak'nor

A Free Jaffa and former servant of Heru-ur. Rak'nor is a formidable warrior and a close friend of Teal'c. Along with Teal'c and Bra'tac, Rak'nor worked tirelessly to ensure the success of the creation of a Free Jaffa nation.

[Vern]

Rules of Engagement (episode)
Upon exiting the Stargate, SG-1 finds itself in the midst of battle.

Red Sky (episode)
The fate of an entire civilization is inadvertently doomed when an off-world Stargate is activated.

Rite of Passage (episode)
A virus implanted by the Goa'uld takes control of Dr. Fraisier's daughter.

Revelations (episode)
SG-1 must come to the defense of their once-powerful allies when the Goa'uld attack an Asgard laboratory.

Redemption (episode)
A tragic event reunite's Teal'c with his son, who demands proof that the Goa'uld can be defeated. O'Neill and Carter launch a risky plan when the SGC comes under attack by the Goa'uld.
In part two Teal'c and Bra'tac make a daring attempt to save Earth that could destroy the Stargate, and young Rya'c must come to their rescue.

[Vern]

Revisions (episode)
The Stargate SG-1 team encounters a planet with a society that has lived for centuries within a computer-controlled bubble environment. Unfortunately, the computer tends to lie--a lot.

Resurrection (episode)
Daniel discovers a human-Goa'uld hybrid and tries to gain her trust.

Reckoning (episode)
The Jaffa Resistance assembles an army to retake the holy city of Ta'kara. Plus, Baal seeks help from Earth when he is faced with a threat common to both parties.

Rising (episode)
SG-1 discover what they believe to be the remnants of the Lost City of the Ancients. A new team lead by Dr. Elizabeth Weir is sent to the distant Pegasus Galaxy to explore.