Goa'uld characters in Stargate

Anubis

Anubis, originally played by David Palffy when he appeared only as a cloaked figure with an obscured face, is an extremely powerful Goa'uld System Lord who replaces Apophis as the main enemy in Stargate SG-1. The character is first mentioned in the season 5 episode "Between Two Fires", although he is not seen in person until "Revelations". In "Reckoning", he is seen in two different host bodies, played by Dean Aylesworth and Rik Kiviaho. In "Threads", in the persona of "Jim", he is played by George Dzundza. Anubis has a tendency to make pronouncements that are excessively melodramatic even by Goa'uld standards; at one point Jack O'Neill comments, "Oh come on, who talks like that?"

Anubis had been banished by the System Lords thousands of years ago for crimes that were unspeakably evil even by Goa'uld standards, and the system lord called Yu had tried to murder him. Anubis was believed to have died thereafter, but in fact he had instead tricked the Ascended being Oma Desala into helping him Ascend. Once his evil became apparent to them, the other Ascended beings "descended" him—but incompletely, allowing him to retain Ancient knowledge and to do everything he had previously been able to do as a regular Goa'uld. Anubis thus becomes an incorporeal being who is given form by a shield. In secret, Anubis gathers his strength and develops advanced technologies that would give him an advantage over the other Goa'uld; he also experiments with creating Ascension-capable humans using a DNA Resequencer. Anubis recruits the Goa'ulds Tanith, Zipacna, and Osiris to further his various goals; in season 5 he subjugates and later annihilates the Tollan, launches a naqahdah asteroid towards Earth, decimates the Tok'ra, and captures Thor. He also has himself reinstated into the ranks of the System Lords (only Lord Yu dissented in the vote) despite having attacked their holdings, with the promise of eliminating the Tau'ri (Humans on Earth and their descendents).

In the season 6 premiere "Redemption", Anubis makes good on his promise by employing an Ancient weapon that would have detonated the naqahdah in Earth's Stargate, which would have wiped out all life on Earth. O'Neill flies the Stargate to a safe distance from Earth before it explodes, and the weapon is destroyed by Rya'c. In, Anubis seeks out six powerful artifacts to power a superweapon on his mothership. SG-1 finds the last artifact, the Eye of Ra, on Abydos, and at Daniel Jackson's behest hands it to Anubis in exchange for sparing Abydos. Anubis uses his superweapon to devastate the collected fleet of the System Lords before breaking his agreement and destroying Abydos; Jackson is stopped from acting against him by the other Ascended beings. In "Fallen", SG-1 lures his mothership to Vis Uban and launches an F-302 attack that disables the superweapon. Anubis then travels to Langara to investigate naqahdriah as an alternate power source for his weapon, based on information he extracts from Jonas Quinn's mind. The System Lords arrive at Langara and destroy his mothership, though Anubis escapes.

In the second half of season 7, Anubis creates a new army of nearly invincible Kull Warriors to replace his Jaffa. He assassinates a number of minor Goa'uld, absorbing their forces into his own in preparation for the upcoming war against the System Lords. In "Lost City", Anubis launches a full-scale assault on Earth with a fleet of over thirty motherships. His fleet is annihilated by the Ancient drone weapons launched from the Antarctica outpost by SG-1. However, Anubis survives in energy form and possesses several SGC personnel in a bid to reach the Stargate. Carter sends him, in the body of Colonel Vasilov, to a frozen wasteland. Anubis eventually frees himself and secretly establishes dominance over Ba'al, possessing a succession of host bodies as each one quickly deteriorates under his influence. During the Replicator invasion of the Milky Way, he plans to use the Dakara superweapon to destroy all life in the galaxy and then repopulate it to his own designs. Anubis continues his plan after the Replicators are destroyed, outmaneuvering the Free Jaffa and conquering Dakara. At the same time, as a man named "Jim", he converses with Daniel Jackson and Oma Desala at an illusory diner between the normal and Ascended planes of reality. "Jim" reveals to Daniel that the reason Anubis was allowed to keep his Ascended memories is to punish Oma, who must watch helplessly as he wreaks havoc on the galaxy. Just as Anubis prepares to use the Dakara superweapon, Oma engages him in battle, ensuring that for all eternity he would be forced to contend with her to the exclusion of everything else.

Apophis

Apophis, played by Peter Williams, is a Goa'uld System Lord and the main villain for most of the first four seasons of Stargate SG-1. He is based on the god Apep of Egyptian mythology. As in mythology, Apophis is the enemy of Ra, and gains power after Ra is killed by Daniel Jackson and Jack O'Neill. Apophis' first appearance on SG-1 is commanding a raid on Earth through the Stargate, in which he abducts a female Airman as a potential host for his queen Amonet. He also raids Abydos for potential hosts, taking Sha're and Skaara. These incidents lead to the restarting of the Stargate Program, and both O'Neill and Jackson joining a mission to Apophis' homeworld, Chulak. Their team escapes death by Apophis with the help of his then-First Prime, Teal'c, though not before witnessing Sha're and Skaara being taken as hosts.

The existence of the Tau'ri now known to him, Apophis launches attacks on Earth that are blocked by the Earth gate's iris. His forces also skirmish with SG-1 on several worlds. Apophis eventually launches a full-scale assault on Earth with two motherships. None of Earth's weapons are effective against them, but SG-1 manages to infiltrate and destroy both. Apophis and his son Klorel escape, though this defeat severely diminishes his standing amongst the System Lords. To strengthen his position, Apophis brainwashes Teal'c's son Rya'c into denouncing his father, and tries to use him in a plot to release a bioweapon at the SGC. Apophis also fathers a Harcesis child with Amonet/Sha're. He is led to believe that Heru-ur took the child, although in reality he has been hidden away by SG-1.

The Goa'uld Sokar soon takes advantage of Apophis' weakness, crushing his forces and capturing him. Apophis manages to escape and seeks sanctuary with the Tau'ri. Severely wounded, Apophis dies at the SGC; in his last moments his host, an Egyptian scribe, emerges for the first time in thousands of years. Apophis' body is returned to Sokar to avert an attack on Earth. Sokar revives Apophis with a sarcophagus for additional torture, eventually sending him to the hellish prison moon of Ne'tu. There, Apophis disguises himself as a mysterious figure named Na'onak and works his way back into power as the First Prime of Bynarr, Lord of Ne'tu. He recognizes SG-1 when they arrive at Ne'tu to rescue Jacob/Selmak. Killing Bynarr, he then interrogates SG-1, Martouf, and Selmak using a hallucinogenic drug (the "blood of Sokar"), hoping that with useful information he can get close enough to Sokar to assassinate him. Apophis escapes to Delmak after Sokar recognizes that he has only false information from his captives. Shortly after, Sokar is killed when the Tok'ra destroy Ne'tu, leaving Apophis in control of his domain.

With Sokar's massive fleet and army, Apophis becomes the most powerful Goa'uld in the galaxy. He attacks and reclaims Chulak, kills Heru-ur and absorbs his domain after a failed attempt at an alliance, and by the end of season 4 stands poised to destroy the System Lords and conquer the galaxy. To avert this, the Tok'ra lure him into a trap at Vorash, using a Stargate connected to a black hole to trigger a supernova that incinerates his fleet. Once again, Apophis survives by taking his mothership into hyperspace after SG-1 captured Ha'tak. Both ships are thrown to another galaxy by the nova, where Apophis' mothership comes under attack by Replicators. Apophis escapes to SG-1's Ha'tak, having brainwashed Teal'c into again serving as his First Prime, but the Replicators infest that ship as well and send it towards the Milky Way. Knowing the threat of the Replicators, SG-1 sabotages the engines so that the Ha'tak will crash into Delmak upon exiting hyperspace. Swarmed by Replicators, Apophis is helpless as his ship plummets into Delmak.

In an alternate reality depicted in "Point of View", Apophis launches a devastating invasion of Earth that is only turned back after the SG-1 of this reality helps their alternates contact the Asgard. Another version of Apophis appears in the alternate timeline of "Moebius", ruling over Chulak. He also captures a team from Earth and has a Goa'uld symbiote implanted into Daniel Jackson to learn about Earth. Apophis appears briefly in Stargate: Continuum as the last System Lord defeated by Ba'al; Teal'c brings him before Ba'al, who executes him by slicing off the top of his head.

David J. Tholen and Roy A. Tucker, two astronomers who are reportedly fans of Stargate SG-1, named a near-Earth asteroid that they co-discovered in 2004, 99942 Apophis as an allusion to the Stargate villain.

Ba'al

Ba'al, played by South African actor Cliff Simon, is a Goa'uld based on the Baʿal of Canaanite religion. He first appears in the season 5 episode "Summit", and becomes a recurring adversary in the remaining seasons of Stargate SG-1 as well as in Stargate: Continuum, making him the longest-running villain in Stargate history. In the show, Ba'al is an intelligent and cunning System Lord, though unlike most of his peers he is rather flippant about his "godhood". He has even stated openly that the goa'uld are not actually gods and know it themselves, "or, at least, some of us do". At a meeting of the System Lords, Ba'al votes to accept Anubis back into their ranks. In "Abyss", he captures Jack O'Neill and tortures him for information by repeatedly killing him and then reviving him in a sarcophagus. Ba'al eventually turns against Anubis along with the other System Lords; due to Lord Yu's senility, he takes command of their combined fleet and destroys Anubis's mothership at Langara. Ba'al proceeds to conquer Erebus and sends an operative to Langara. In "Avenger 2.0", Ba'al modifies Jay Felger's computer virus to disable the Stargate network, giving him an advantage due to his large fleet.

After Anubis's fleet is destroyed in "Lost City", Ba'al locates Tartarus and gains control of the Kull Warriors. With this substantial advantage, he wages a highly successful war against all the other System Lords, driving them to the brink of defeat. However, at some point Anubis returns and secretly forces Ba'al back into his service, much to Ba'al's displeasure. During the Replicators' invasion of the galaxy, Ba'al contacts the SGC to tell them of Anubis's plan to use the Dakara superweapon to destroy all life in the galaxy. When Anubis orders Ba'al to retake Dakara from the Jaffa rebellion, Ba'al stalls as much as he can and assists Samantha Carter and Jacob/Selmak in calibrating the superweapon to destroy the Replicators. He also provides a means to dial all the Stargates in the galaxy simultaneously through the help of a minor Goa'uld named Nerus. After the Replicators are defeated, Ba'al beams away after his mothership is stormed by rebel Jaffa. Anubis was aware of Ba'al's treachery, though it was of little concern to him.

With his traditional power base gone, Ba'al travels to Earth and takes over the Trust, which had already been infiltrated by the Goa'uld. Ba'al establishes himself as a wealthy businessman and adopts Earth customs and fashions. He informs the SGC that he only intends to live out his exile in peace (and that he has also planted naqahdah explosives as insurance). It is revealed that Ba'al has made multiple clones of himself; one of these clones is captured and executed by the Free Jaffa Nation, but many more remain. After realizing the threat posed by the Ori, Ba'al begins a campaign to battle the invaders for control of the galaxy. He brainwashes half the Jaffa High Council, asserting that only his leadership would allow the Jaffa to resist the Ori. Teal'c and Bra'tac uncover Ba'al's plot, and the Ba'al clone responsible is killed by SG-1. Ba'al also attempts to build his own private empire by stealing Stargates. The SGC uses an unwitting Nerus to locate and disable the Ba'al clone's Ha'tak, which is destroyed by the Lucian Alliance after the Odyssey retrieves the Stargates.

In "Insiders", the supposed real Ba'al turns to the SGC for help in neutralizing his clones, who he claims have turned against him. However, this is nothing more than an elaborate ruse to gain access to a list of planets where the Sangraal might be hidden. Ba'al had brainwashed NID agent Malcolm Barrett in preparation for his breakout at the SGC, and most of the Ba'al clones escape once they have the information. SG-1 eventually encounters a Ba'al clone while searching for the Sangraal. He, along with Adria, are forced to work with SG-1 to overcome Morgan Le Fay's various defensive measures protecting Merlin's resting place. In "Dominion", Ba'al intercepts SG-1's plan to capture Adria and implants one of his cloned symbiotes within her. He also massacres most of his clones using symbiote poison, though it is by no means certain whether there are any more. The Ba'al symbiote is extracted by the Tok'ra after SG-1 recaptures Adria, though not before it releases a toxin that eventually forces her Ascension. In Stargate Continuum, the last Ba'al clone has been captured, though the real Ba'al changes history by going back in time and stopping the Stargate Program from happening. In the alternate timeline, he defeats the System Lords and prepares to conquer Earth, only to be betrayed and killed by his queen Qetesh onboard his flagship. SG-1 repairs the timeline using Ba'al's time machine, and Cameron Mitchell travels back to before Ba'al enacts his plan and kills him when he appears. With the timeline restored, the Tok'ra extract the symbiote from the last Ba'al clone. However, the cloned host survives and is able to live on.

Cliff Simon met with executive producers Robert C. Cooper and Brad Wright and auditioned eight months before the character Ba'al was created for the series. Simon, Cooper and Wright came to an agreement to wait until they found the right character for Simon in the show. Simon said "I was very lucky," when talking about his character in an interview with The Sci Fi World. According to portraying actor Simon, Ba'al was his most "interesting" he's done because of Ba'al's character development and diversity among others. Simon felt that he needed to diversify the character to make it more exciting, as he put it, "if you’re always bad, it gets pretty boring." He wanted to change the development of the character, the writing staff eventually agreed with him and started fleshing out his character.

Cronus

Cronus, played by Ron Halder, was one of the most influential of the System Lords, named for Cronus in Greek mythology. He was the one who banished Sokar and was the mortal enemy of Apophis. Teal'c's father was Cronus's First Prime; Cronus ordered him to fight an unwinnable battle against a more powerful Goa'uld. After his inevitable defeat, Cronus executed him by crushing his symbiote, causing its blood to mix with his in a slow and painful death. Thus, Teal'c vowed that he would one day become the First Prime of Apophis, Cronus' enemy. Cronus sent the Ashrak that hunts Jolinar of Malkshur in "In the Line of Duty". He also developed kor mak bracelets for use in transporting prisoners.

In "Fair Game", Cronus, Nirrti, and Yu travel to Earth to negotiate Earth's entry into the Protected Planets Treaty. During the talks, Teal'c is called into Cronus's room, whereupon both are attacked by an invisible force. Although it is initially feared that Teal'c attacked Cronus due to their enmity, eventually Nirrti is found to be responsible. Samantha Carter is able to heal Cronus's wounds using a Goa'uld healing device, salvaging the talks, and Nirrti is turned over to Cronus. In "Double Jeopardy", Cronus conquers Juna and captures SG-1, but is shocked to find that they are in fact android duplicates created by Harlan, who seeks out the real SG-1 for help. Both Teal'c and his android counterpart confront Cronus, though Cronus overpowers both of them. As he prepares to crush Teal'c's symbiote, he is shot in the back by android Teal'c, with the words "for our father". SG-1 captures Cronus's Ha'tak, which is later used in a Tok'ra plan to lure Apophis's fleet into a trap at Vorash. Cronus appears briefly in the alternate timeline of Stargate: Continuum as one of Ba'al's lieutenants; he is later revealed to have been conspiring with Qetesh against Ba'al.

Nirrti

Nirrti, played by Jacqueline Samuda, is a Goa'uld named for Nirṛti in Hindu mythology. She is interested in engineering an advanced human host (a hok'taur) for herself. On the planet Hanka, she wipes out the entire population with a deadly pathogen except for one girl, Cassandra, whom she modifies into a living bomb knowing that SG-1 would take her back to Earth. She once used a similar tactic against her enemy Apophis. Cassandra is only saved through quick thinking by Samantha Carter. Nirrti first appears in person in "Fair Game", in which she, Cronus, and Yu arrive on Earth to negotiate Earth's entry into the Protected Planets Treaty. During the talks, she attempts to murder Cronus and frame Teal'c, using a personal stealth device based on Reetou phase-shifting to move around the base. Yu is outraged when told that she has kept this technology hidden from the System Lords; Nirrti flees, but is captured and handed over to Cronus.

Nirrti escapes after Cronus is killed by SG-1. When Cassandra begins to manifest telekinesis and life-threatening physiological changes, Nirrti secretly follows SG-1 from her lab back to Earth to learn more. She is captured after Cassandra senses her presence, but she barters her freedom for healing Cassandra. Nirrti expresses surprise to O'Neill that they honor the agreement, stating that she doubts she would have done the same. In "Metamorphosis", a Russian SG team discovers Nirrti's new base, where she is using an Ancient DNA resequencer to experiment on the local population under the guise of helping them. Although they have been physically deformed by the device, she has given them abilities such as telepathy and telekinesis. Believing themselves responsible for the situation, the SGC authorizes Nirrti's assassination. All does not go as planned when Nirrti's subjects capture SG-1, but they turn against her after one of them, Eggar, reads her mind at SG-1's suggestion. Another subject, Wodan, kills her by telekinetically breaking her neck. Nirrti appears briefly in the alternate timeline of Stargate: Continuum as one of Ba'al's lieutenants.

Osiris

Osiris, played by Anna-Louise Plowman, is a Goa'uld based on the Osiris of Egyptian mythology. Thousands of years ago, he was banished in a stasis jar along with his queen Isis by his brother Seth. Osiris escapes when the jar is opened by archaeologist Sarah Gardner, a former colleague and love interest of Daniel Jackson. He possesses her, and escapes Earth in a hidden starship. Osiris is recruited by Zipacna into the service of Anubis, and represents him at a summit of the System Lords. Daniel, who had infiltrated the meeting, uses the Re'ol chemical on her to prevent her from exposing him, and attempts to capture her in Yu's scoutship. However, Yu happens upon them and releases Osiris, who stabs him while Daniel escapes. In "Revelations", Osiris commands a Ha'tak charged with locating the base of the Asgard Heimdall, and is able to defeat Thor's mothership and capture him due to Anubis' shield enhancements. She is momentarily thrown when Carter tells her that Daniel had died. Osiris is forced to retreat with the arrival of Asgard reinforcements. Osiris returns to Earth in "Chimera", using a Goa'uld memory device on Daniel while he sleeps in an attempt to find the location of the Lost City of the Ancients in his mind. She is eventually discovered and captured, and the symbiote is extracted from Sarah, freeing her at last.

Ra

Ra is the villain in the original Stargate movie, and is established in the television show Stargate SG-1 as a Goa'uld. The character is based on the Ra of Egyptian mythology. He is played by Jaye Davidson in the film and Jay Williams in the series. In some scenes of the movie, the outline of Ra's original humanoid form can be seen. Supplementary materials for Stargate SG-1 explained this by retconning Ra as a canonical Goa'uld, with his previous host being an Asgard named Famrir, whose genetic degradation was not as extreme as seen in the series to explain the visual difference, due to the Asgard's need to clone themselves to propagate instead of via sexual reproduction, steadily whittling away their appearance with each progressive clone as a result. This would also give some explanation as to how Ra could have become Supreme System Lord, given the access the Ra symbiote would have to his host's knowledge of Asgard technology, which was far superior even to that of the Goa'uld, something he would jealously guard.

According to Stargate mythology, 10,000 years ago Ra voyaged across the galaxy searching for a new host that could sustain his dying form. He discovered Earth and found the native humans easy to repair using his advanced technology. He possessed the body of a young boy, and ruled over the planet as a god. During his reign, he seeded humans throughout the galaxy using the Stargate. Ra was the most powerful and cunning of the Goa'uld, holding the title of Supreme System Lord. His Queen was Hathor, his son was Heru-ur, and his brother (and enemy) was Apophis. Ra also defeated the Tok'ra Queen Egeria, and battled the Goa'uld Shaq'ran.

Five thousand years ago, the people of Earth rebelled against Ra and buried the planet's Stargate in Egypt. In order to avert another such uprising, Ra outlawed reading and writing on his other planets, including Abydos. In the Stargate film, an Earth team led by Colonel Jack O'Neil (his name was spelled O'Neil in the film and changed to O'Neill in the series) travels to Abydos after the Stargate is activated, to reconnoiter the area and if necessary close the way to Earth with a nuclear bomb. They are captured by Ra's forces upon his return to the planet. Ra plans to send the bomb back to Earth along with a quantity of naqahdah, which will amplify the explosion. O'Neil and his team escape and eventually incite a successful rebellion amongst the Abydonians. As Ra abandons the planet, O'Neil and Jackson teleport the active bomb to his ship by way of a ring transporter, destroying it and him. Ra's death draws the attention of the other Goa'uld to Earth, and creates a power vacuum amongst the System Lords that allows first Apophis, and later other System Lords, to become more powerful.

Although mentioned numerous times, Ra has only appeared once on Stargate SG-1, in masked form, in the season 8 episode "Moebius". In that episode, SG-1 travels back in time to steal a ZPM from Ra in Egypt, and inadvertently changes history into one where Ra took the Stargate with him after the rebellion on Earth. The original timeline is restored after a second version of SG-1 travels back and ensures that the Stargate is left behind. An unmasked Ra appears briefly in the alternate timeline of Stargate: Continuum as one of Ba'al's lieutenants.

Sokar

Sokar, played by David Palffy, is a Goa'uld who replaces Apophis as the principal enemy of SG-1 for the first half of the third season. He is named for the Seker of Egyptian mythology. Sokar only appears in person in "Jolinar's Memories" and "The Devil You Know", although his magnified voice is heard in "Serpent's Song". Sokar is an ancient Goa'uld who once ruled the System Lords until he was defeated by an alliance that included Ra, Apophis, and Cronus. In those times, his host body was that of an Unas. Sokar has posed as the god of death on many different worlds, and Satan is one of his guises. He terraformed the moon Ne'tu, in orbit around his homeworld Delmak, into a literal version of hell to serve as a prison.

Apophis' defeat at the hands of SG-1 paves the way for Sokar's return to power. Sokar captures the weakened Apophis and tortures him, but Apophis escapes and demands sanctuary amongst the Tau'ri. Sokar subsequently launches an attack against the SGC by using a particle beam to melt through the Stargate iris at the SGC. At the urging of the Tok'ra, Apophis' body is returned to Sokar, who revives him with a sarcophagus for further torture. Sokar eventually amasses the largest fleet in the entire Goa'uld domain, and is poised to launch an all-out attack on the System Lords that the Tok'ra believe will succeed. As this would give Sokar control of the galaxy and make him unstoppable, the Tok'ra enact a plan to assassinate him by blowing up Ne'tu while Sokar's ship is in orbit, which is complicated by the capture of Jacob/Selmak. At the same time, Apophis also attempts to assassinate Sokar by first currying favor with him while in disguise. Although Apophis fails, he manages to escape before Ne'tu explodes, giving him control of Sokar's massive army.

Tanith

Tanith, played by Peter Wingfield, is a Goa'uld symbiote incubated by the Jaffa priestess Shan'auc. While within her, he communicates with her and leads her to believe that he intends to renounce the Goa'uld's evil ways, causing her to defect to the SGC and eventually the Tok'ra. However, once he matures and blends with his host Hebron, he murders Shan'auc for betraying her true god. Teal'c, who loved Shan'auc, swears revenge, but is stopped by the Tok'ra, who know of Tanith's duplicity and are using him to feed misinformation to the System Lords. In "Exodus", having set a trap for Apophis, the Tok'ra have no more use for Tanith and intend to extract him and let him die on the sands of Vorash. Tanith however escapes to Apophis, bringing Teal'c with him. He escapes again from Apophis' ship after the Tok'ra and SG-1 spring their trap and destroy Apophis' fleet with a supernova.

In "Between Two Fires", Tanith is revealed to have switched masters to Anubis, who remains unnamed at this juncture. He travels to Tollana on one of Anubis' enhanced Ha'taks, which are immune to Tollan ion cannons, and extorts the Tollan Curia into building weapons of mass destruction equipped with phase-shifting devices that will allow them to penetrate the iris on the Earth Stargate. After Narim destroys the weapons, Tanith commands an assault that annihilates the Tollan. Tanith's final appearance is in "48 Hours", where he encounters SG-1 on a scouting mission. He attacks them from his Al'kesh, but Teal'c kills him by firing his death glider staff weapon directly into the bomber's cockpit, avenging Shan'auc.

Yu

Yu, played by Vince Crestejo, is the eldest of the System Lords. Unlike the other System Lords, he didn't directly pretend to be a god, but took position as one of China's earliest emperors. Among all the Goa'uld leaders, it is notable that he did have several positive influences during his reign. In the show, he has been introduced as Yu the Great in "Fair Game", and the Jade Emperor, the exalted Yu Huang Shang Ti in "Summit", who are separate figures in Chinese mythology.

Yu is a pragmatic villain and the System Lord most willing to deal with Earth; while certainly no friend of the Tau'ri, his galactic interests lie far from Earth and he has cooperated with the SGC when it has suited him. His first appearance is in "Fair Game", when he travels to the SGC along with Cronus and Nirrti to negotiate Earth's entry into the Protected Planets Treaty. Yu supports Earth's entry into the treaty after Nirrti is found to have betrayed the System Lords. In "Summit" and "Last Stand", Yu attends a meeting of the System Lords to discuss a mysterious new threat. Daniel Jackson infiltrates the meeting alongside him, using the Re'ol chemical to fool Yu into believing he is his lo'taur (personal human servant). After Osiris' surprise appearance, Yu is the only one of the System Lords present who votes against readmitting Anubis into their ranks.

After surviving an attack by Osiris, Yu begins a lone battle campaign against Anubis and his System Lord supporters. His forces manage to hold their own despite facing superior numbers and technology, to the surprise of the SGC and the Tok'ra. He also defeats a rebel Jaffa assault on his homeworld led by Teal'c, which was planned by Kytano (in fact the Goa'uld Imhotep in disguise). Yu allows Teal'c to return to the Jaffa camp with the truth about Kytano's identity. In "Abyss", he launches an attack on Ba'al's secret outpost based on information provided by the SGC; this attack allows Jack O'Neill to escape Ba'al's captivity.

In, Yu convinces the other System Lords to join him in opposing Anubis and claiming the powerful Eye of Ra for themselves. Their collected fleet confronts Anubis' mothership over Abydos, but are decimated after Anubis activates his superweapon. In "Fallen", Yu agrees to bring the full force of the System Lords down on Anubis once SG-1 destroys his superweapon. However, he inexplicably takes his fleet elsewhere. His First Prime, Oshu, reveals to Teal'c that Yu's mind is failing due to old age, and furthermore he is no longer able to take a new host. Thus, they persuade Ba'al to take command of the fleet, which destroys Anubis' mothership over Langara. Yu again travels to the SGC in "New Order", alongside Amaterasu and Camulus, to negotiate a new arrangement with the Tau'ri against the threat of Ba'al. However, his mind has deteriorated further, and Oshu must speak for him. The System Lords' war against Ba'al goes poorly, and eventually Yu and Amaterasu begin to rally their armies for a final stand. In "Reckoning", Yu and the last of the System Lords receive Ba'al's emissary, who demands their surrender. However, the meeting is interrupted by Replicator Carter, who kills Yu as the first act of her invasion of the Milky Way. Yu appears briefly in the alternate timeline of Stargate: Continuum as one of Ba'al's lieutenants.

Yu's name has served as a source of comic relief on the show, to such a degree that in the beginning of season 8, when Dr. Jackson briefs Dr. Weir regarding Yu's impending arrival on Earth to negotiate a new treaty in the wake of the destruction of Anubis' fleet, Jackson stops her dead in her tracks as she was presumably about to make a joke about Yu's name by saying, "Don't... every joke, every pun, done to death...".

Minor characters