Arkad - Ancients

The Ancients are the original builders of the Stargate network, who by the time of Stargate SG-1 have ascended beyond corporeal form into a higher plane of existence. The humans of Earth are the "second evolution" of the Ancients. The Ancients (originally known as the Alterans) colonized the Milky Way galaxy millions of years ago and built a great empire. They also colonized the Pegasus galaxy and seeded human life there before being driven out by the Wraith. The civilization of the Ancients in the Milky Way was decimated thousands of years ago by a plague and those who did not learn to ascend died out. With few exceptions the ascended Ancients respect free will and refuse to interfere in the affairs of the material galaxy. However their legacy is felt profoundly throughout the Stargate universe, from their technologies such as Stargates and Atlantis to the Ancient Technology Activation gene that they introduced into the human genome through interbreeding.

• Ganos Lal or Morgan le Fay, played by Sarah Strange (season 10) – An ascended Ancient who would give rise to the Arthurian legend of Morgan le Fay. Her fictional backstory closely links her to her fellow ascended Ancient Myrddin (Merlin), who aimed to construct a weapon to fight the Ori that also posed a danger to the Ancients. Morgan le Fay is first referenced in season 10's "Morpheus" and first appears in person in "The Pegasus Project" where she poses as a hologram in Atlantis. She gives SG-1 information about the location of Merlin's weapon, the Sangraal, but the Others banish her for this action. Morgan le Fay is mentioned again in "The Quest" and returns in Stargate: The Ark of Truth to help SG-1 in their fight against Adria in the Ori galaxy. She is last seen engaging Adria in an eternal battle.
• Moros, also known as Myrddin or Merlin, played by Matthew Walker (season 9–10) – The High Councilor of Atlantis during the days of the first siege of the city, and is one of the most influential Ancients in the series. Moros is named after Moros from Greek legend, the personification of impending doom and destruction, while his name Merlin refers to the Arthurian legend. Merlin is introduced in the Stargate Atlantis season 1 episode "Before I Sleep", where an alternate Elizabeth Weir travels through time and meets him as Moros during his days on Atlantis. A tablet Merlin created thousands of years ago is found in season 9's "Avalon" and sets the Ori arc of SG-1 in motion. Merlin appears as a hologram in "Avalon", season 9's "Camelot" and season 10's "The Pegasus Project", providing information about his background and his motivations. As revealed in season 10's "The Pegasus Project", SG-1 must find a weapon that Merlin sought to construct to defeat the Ori, the Sangraal. On this quest, SG-1 finally find Merlin in stasis in season 10's "The Quest" and awaken him. His body dies shortly afterwards, but his transferred consciousness remains in Daniel Jackson until "The Shroud" to complete the building of the Sangraal. • Matthew Walker was nominated for a Leo Award in 2007 for "Best Supporting Performance by a Male in a Dramatic Series" for this role.
• Oma Desala ("Mother Nature"), played by Carla Boudreau (season 3) and Mel Harris (seasons 5, 8) – An Ascended being who goes against the ways of the Ancients. It is unclear if she is an Ancient herself, as the Ancients Orlin and Merlin give different accounts of knowing Oma. Oma is responsible for once helping the fallen System Lord Anubis, the main SG-1 antagonist between seasons 5 through 8, ascend. Although the Ancients banished her for her actions, Oma remains convinced of her responsibility to guide those beneath to the "Great Path" of enlightenment, even if this interferes in the lower planes of existence. Oma therefore only guides individuals, leaving the final decision to travel the great path to them. SG-1 first encounters Oma Desala on their search for Shifu in season 3's "Maternal Instinct". Oma eventually guides Shifu to ascension in season 4's "Absolute Power". Oma is involved in Daniel Jackson's ascension in "Meridian" and forceful de-ascension in "Fallen", and also helps the entire Abydonian population ascend after Anubis's attack in season 6's "Full Circle". Oma Desala last appears in season 8's "Threads", sacrificing herself to enter an eternal battle with Anubis to prevent him from wreaking further havoc on the galaxy. • Mel Harris's teenage son was a Stargate SG-1 fan and introduced her to the series. The Stargate producers offered her the part when she was visiting the set visit while in Vancouver for another job. The best direction she got for playing this almost "omniscient" character was that she was not like others and was a "being" of her own.
• Orlin, played by Sean Patrick Flanery (season 5) and Cameron Bright (season 9, child) – An outcast Ancient whom SG-1 encounters on the dead planet Velona in season 5's "Ascension". He once broke the rules of the Ancients by giving advanced technology to the planet's people, who immediately abused it. After his staying on Earth and developing feelings for Carter, he tries to stop the Earth research of the same weapon and is redeemed and re-ascended by the Ancients. Orlin returns in the form of a human child to retain his Ancient knowledge longer in season 9's "The Fourth Horseman" and informs Stargate Command of the feud between Ancients and Ori, and false promises of ascension and religion. He suffers significant brain damage and is eventually interned in a mental institution on Earth.