501 - ENEMIES

Synopsis:
Trapped in another galaxy with little chance of returning home. SG-1's ships is taken over by Apophis. As is things weren't worse enough, Teal'c serves Apophis and the Replicators manage to infest the ship as well.

Goa'uld Appearances:
Apophis.

502 - THRESHOLD

Synopsis:
Teal'c must undergo a dangerous ritual without his symbiote in order to free himself from the control of Apophis' brainwashing.

Goa'uld Appearances:
Apophis, Ra(mentioned).

503 - ASCENSION

Synopsis:
After discovering an ancient weapon used to defeat the Goa'uld on another planet, Carter is stalked by a strange individual and learns that he may be more that he seems.

Goa'uld Appearances:
None specifically mentioned.

504 - THE FIFTH MAN

Synopsis:
O'Neill and Lt. Tyler are trapped on another planet under siege from a powerful and previously unknown System Lord. Carter and Daniel return to base to be told that Lt. Tyler doesn't exist... just who is Lt. Tyler?

Goa'uld Appearances:
None specifically mentioned.

505 - RED SKY

Synopsis:
SG-1 gate to a planet and realise that their arrival is causing the sun that this planet is orbiting to go nova. The Asgard are called in but cannot help, risking a war with the Goa'uld.

Goa'uld Appearances:
None specifically mentioned.

506 - RITE OF PASSAGE

Synopsis:
Cassandra is ill and asks to return to her planet for a special ritual. It is discovered that Nirrti has been experimenting with the local population and the team must find her to cure Cassandra.

Goa'uld Appearances:
Nirrti.

507 - BEAST OF BURDEN

Synopsis:
The Unas are capture and forced into slavery by a race of humans who freed themselves previously from the Goa'uld. SG-1 must create a revolt to free themselves and the ensalved Unas.

Goa'uld Appearances:
None specifically mentioned.

508 - THE TOMB

Synopsis:
Sg-1 and a Russian team enter an ancient ziggurat previously entered by another team. They are confronted with an evil and mad Goa'uld possessing an artifact of great power.

Goa'uld Appearances:
Marduk.

509 - BETWEEN TWO FIRES

Synopsis:
The Tollans are eager to share technology after years of refusing to share any advanced technology. Narim and SG-1 discover that their recent good will may be motivated by something much more sinister.

Goa'uld Appearances:
Tanith, Unamed Goa'uld(mentioned).

510 - 2001

Synopsis:
Sg-1 encounter an advanced race called the Aschen who offer an alliance and technological help that could help Earth defeat the Goa'uld. An ominous message from the future is questioned and the true intentions behind their good faith are yet to be known.

Goa'uld Appearances:
None specifically mentioned.

511 - DESPERATE MEASURES

Synopsis:
Carter is kidnapped by a rich business man who wishes to be cured of a disease using a Goa'uld symbiote. O'Neill and Maybourne reluctantly team up to find Carter.

Goa'uld Appearances:
Adrian Conrad.

512 - WORMHOLE X-TREME!

Synopsis:
A new televisions series feaatures a story particularly similar to the Stargate Program secretly being run by the government. SG-1 track down Martin who is at the source of this revolutionary series as an alien ship is bound for Earth.

Goa'uld Appearances:
None.

513 - PROVING GROUND

Synopsis:
A group of promising young cadets are put through their final simulations when it becomes apparent that the SGC has been compromised by aliens forces. O'Neill must work with them to retake the facility from... Daniel Jackson!

Goa'uld Appearances:
Pelops(mentioned).

514 - 48 HOURS

Synopsis:
After facing Tanith, Teal'c is literaly trapped within the stargate's structure, giving Carter and an arrogant scientist a limited time frame to save him. Meanwhile, Daniel Jackson and Major Davis go to Russian and negociate to acquire the original dialing device.

Goa'uld Appearances:
Tanith.

515 - SUMMIT

Synopsis:
The Goa'uld System Lords attend a summit in order to create an alliance against a powerful Goa'uld causing massive damage to their holdings. Daniel goes undercover in order to take out the Goa'uld leadership once and for all. Things get complicated when an unexpected guest makes a appearence at the summit.

Goa'uld Appearances:
Yu, Baal, Olokun, Bastet, Kali, Svarog, Morrigan, Osiris, Zipacna, Cronos(mentioned), Sokar(mentioned), Anubis(mentioned), Nirrti(mentioned).

516 - LAST STAND

Synopsis:
Osiris puts the System Lords against an ultimatum concerning Anubis' forces and must decide to include him among their alliance. Meanwhile, Zipacna is attacking the Tok'ra planet of Revanna in search of their new and powerful weapon.

Goa'uld Appearances:
Yu, Baal, Olokun, Bastet, Kali, Svarog, Morrigan, Osiris, Zipacna, Cronos(mentioned), Sokar(mentioned), Anubis(mentioned).

517 - FAIL SAFE

Synopsis:
A large ateroid is bound for Earth and SG-1 repair a damaged cargo ship in the hopes of detonating it before it hits the planet. Once on the asteroid, they realise that their task may not be as simple as they thought.

Goa'uld Appearances:
None specifically mentioned(Anubis implied later in season six).

518 - THE WARRIOR

Synopsis:
A brave Jaffa warrior creates a vast army of rebel Jaffa and seeks the help of Earth against the Goa'uld System Lords. His ideals seem just, but his methods a quickly questioned by SG-1.

Goa'uld Appearances:
Yu, Imhotep, Zipacna(mentioned), Nirrti(mentioned).

519 - MENACE

Synopsis:
A young woman is discovered to be an androind and brought to the SG-1. Considering it to be the find of the century, they later realise this android may be the source of a powerful, and up to date invincible, enemy.

Goa'uld Appearances:
None.

520 - SENTINEL

Synopsis:
The planet Latona is facing invasion by the Goa'uld when a weapon called the Sentinel was deactivated by the rogue NID stargate teams. SG-1 must team up with two of their former members in order to prevent the power System Lord Svarog from conquering the planet.

Goa'uld Appearances:
Svarog.

521 - MERIDIAN

Synopsis:
Daniel Jackson is bombarded by dangerous radiation and is sure to die. His only hope is taking advice from Oma Desala, whom may yet save him... as well as change him forever.

Goa'uld Appearances:
None.

522 - REVELATIONS

Synopsis:
Osiris captures Thor while searching for a hidden Asgard laboratory. SG-1 are asked to help out and meet Heimdall in order to plan their release of Thor. Meanwhile, Osiris asks the powerful Anubis to come an interrograte Thor is the hopes of acquiring all his secrets.

Goa'uld Appearances:
Osiris, Anubis, Yu(mentioned).