Rà was the main villain in the 1994 science-fiction film Stargate. He was played by Jaye Davidson
Ra was the last of an ancient technologically sophisticated race belonging to the planet Abydos. In time his body became weaker and began to die, but having the power to migrate into other bodies, he eventually came to Earth in pre-history and took over the body of a young boy. He enslaved the human race and and was worshiped as a god.
He created a portal/device called a Stargate that was able to transport any matter from a planet to another at the speed of light, including humans. Eventually, the slaves rebelled against his tyranny and forced him to leave the planet and the Stargate behind. His teachings gave birth to the Egyptian culture.
The Stargate was later found in Egypt in 1929, and eventually taken to a secret underground base to be studied. In 1994 a symbolist and archaeologist named Daniel Jackson was called in to decode the seventh symbol embedded on the portal in order fro it to function. After decoding it the government sent Jackson and a military unit through the Stargate to see what was on the other side. They were transported directly to Abydos but were unable to get back to Earth because Jackson couldn't decipher one of the symbols.They eventually met the human population of Abydos and learned about the existence of Ra. Soon enough Jackson came to know about his evil tyranny and convinced the Abydonians to stop worshipping Ra as a god and rebel. In the meantime, Rà stole a bomb taken through the stargate by Col. Jack O'Neil and modified it to his advantage to destroy the living rebels on the planet. Ra tried to escape yet again but Jackson and O'Neil activated the ring transporter (teleportation device) of Ra's ship and sent the bomb up to the leaving craft blowing it up and killing the evil ruler.
Depiction in Stargate SG1
Ra has also appeared a couple of times in the TV series Stargate SG1 although it is important to know that due to the series being created by a different crew than the motion picture there are many inconsistencies in continuity between the two products. In the film, Ra was the last of an alien humanoid race while in the series he is a member of a parasitic serpent-like species called Go'auld.
In the film, it was never explained how Ra could migrate from a body to another while in the series it is stated that the Go'auld slip inside the host's body and entangle around the spine thus controlling the Host's brain. In the series, it is stated that the Stargate device wasn't created by Ra's race but belonged to a pre-human race called the Ancients.