The System Lords and Goa'uld
This page contains information on all the major System Lords. There are lot more than mentioned here.
Serpent Guards
Serpent Guards are Jaffa loyal to Apophis. All Jaffa carry a young Goa' uld, called a symbiote, in their stomach. Serpent Guards have fold down visors and carry Staff weapons. They are as weak as a human though.
Horus Guards
Horus guards were the most common type of enemy jaffa. They served Ra, Heru'ur, Amaunet and Hathor
Ra
Being the first System Lord to be seen, Ra (Played by Jaye Davison) only appeared in the original 1999 movie and episodes where the timeline was altered (Including the movie 'Continuum'). He was the first System lord seen to have used a sarcophagus and a hand device. His minions were Serpent guards.
Apophis
Apophis was the first System Lord to be encountered by the SGC after the Abydos mission. He came to earth through the Stargate trying to find a host for Amaunet. (A host is a human or other creature that a goa'uld can control). He eventually used Daniel's wife, sha're for Aaunet's task. Apophis died twice. Once because of Old age but was ressurected by a sarcophagus owned by Sokar. The second time, he was on a ship that was about to crash into a planet, with Replicators surrounding him.
Hathor
Hathor was trapped in an egyptian pyramid for thousands of years, until she was awaken by Archaeologists. Hathor had the power to seduce any men she wanted and make them be her minions. She was a goa'uld queen who incubated young symbiotes. The second time she encountered SG-1, Hathor created an elaborate mock-up of the SGC, but was outwitted. She was killed by Jack 'o' Neil.
Heru' ur
Heru 'ur was a System lord who was seen personally leading his own jaffa into battle. He was the son of Ra and Hathor. His Jaffa were horus guards (not to be confused with Apophis' and Ra's minions, Serpent Guards.) He was very stubborn and was hated by Apophis. He died when his ship was blown up by Apophis.
Osiris
Osiris was trapped in a jar for thousands of years, until Sg-1 encounteredd it and it took Daniels girlfriend, Sarah, as host. She flawed the Tok'ra plan to kill every system lord using gas. She served Anubis and tried to find the location of Atlantis by manipulating Daniel's Dreams. She was one of two System lords which SG-1 managed to free the human host.
Anubis
Anubis was a half ascended, half Goa' uld ancient. He tried to destroy Earth numerous times, including sending a huge meteorite on a crash course for earth. When Daniel Jackson was ascended, he tried to destory Anubis, but was stopped by Oma Desala. He and Jonas were later captured by Anubis, but managed to escape. Anubis' fleet was destroyed by the Antarctic weapons platform on Earth. But, Anubis was half ascended and caused havoc in the SGC after he could posess bodies. He tried to later destory the whole Galaxy using the Dakara superweapon. Oma Desala eventually challenged Anubis to eternal combat.
Nirti
Nirrti was trying to find the perfect host. She sent Cassandra, a living bomb, to the SGC to try blow it up. But Cassandra was defused and adopted by Janet Fraiser. Nirrti had many secret labs around the milky way galaxy. She managed to capture SG-1 and accidentaly gave Jonas Quinn precognative abilities. Nirrti was killed by her own mutants.
Ba'al
Ba'al was the last surviving system lord. He was first encountered by Jack 'o' neil when he (Jack) was tortured to try and get informaion from his former Tok'ra, Ba'al was hated by all the other System lords and sometimes caused the Taur'i (humans) and the other System lords to work together to defeat him. Ba'al created numerous clones of himself, this being very annoying. Ba'al's Symbiote was removed from his human host in the movie 'Continuum' after failing to alter the timeline.