Lantean

"Why'd they leave? Um, who knows? We know the Ancients on Earth were suffering from a plague. Uh, maybe some of them were trying to start over, seeding life in a new galaxy."

- Daniel Jackson

The Lanteans, also known as the Atlanteans and the Ancestors, were those Ancients who left Earth in the city-ship Atlantis and settled in the Pegasus galaxy. They were directly responsible for the emergence of the Asurans and the Wraith.

Arrival
"... in the hope of spreading new life in a galaxy where there appeared to be none. Soon the new life grew, prospered...In time, a thousand worlds bore the fruit of life in this form."

- Melia

After leaving the Milky Way and arriving in the Pegasus galaxy, the Ancients settled on a planet named Lantea, and came to be known as the Atlanteans or Lanteans. Finding Pegasus devoid of sentient life, the Atlanteans seeded Pegasus with humans. The humans seeded by the Ancients came to call them the Ancestors.

The Great Scourge
"The Lanteans were powerful but careless"

- Todd

However, one of the planets seeded held a creature called the Iratus bug, which began feeding off the humans seeded there. Eventually, the Iratus bugs began to mutate, taking on advantageous human characteristics. This resulted in a hybrid species, the Wraith. For over a century, the Atlanteans and the Wraith warred with each other.

While the Atlanteans had the advantage of technological superiority, the Wraith were too many. Desperate, they turned to extreme measures, such as Project Arcturus, an attempt to extract Zero Point energy from their own universe, and created the Asurans, nanites designed to destroy the Wraith from within. Both attempts failed, with disastrous consequences.

Seeing no way to win the war, the remaining Ancients submerged Atlantis and returned via Stargate to Earth.

End of the Lanteans
"When we first abandoned Atlantis all those millennia ago, the Earth was so harsh, its people so primitive by comparison, there was no hope of living among them as Lanteans or rebuilding our society. So instead, we spread out to many lands, some of us planting a few small seeds of civilization among the first tribes of man. Others making their way to the Stargate at your southern pole. Still others choosing to live the remainder of our lives in seclusion and meditation. Merlin and I both chose the latter path."

- Ganos Lal

Upon arriving at Earth, they quickly realized that there was no hope of rebuilding their society, as Earth was too harsh and the Humans too primitive. Some chose to go to other worlds, others secluded themselves in meditation and ascended, and others chose to join the native humans, where they reintegrated back into human society. This is how several humans, such as Jack O'Neill and John Sheppard have "the Ancient gene" required to use Ancient technology.

The Ancients that left Earth were later part of the Alliance of Four Great Races, with the Asgard, the Furlings, and the Nox. It was after their return to Earth that they developed some of their most advanced technology, far surpassing that of the Asgard and other races. This includes: transport beams and the ability to beam entire structures through a Stargate, most of Merlin's technology (excluding the Sangraal) such as the molecular construction device (used to build anything at the molecular level using one's mind), and solid holograms (which could physically interact with matter).

Architecture
After traveling to the Pegasus Galaxy, the Ancients built structures of metal, and they were quite large. Atlantis, the centerpiece of their society, was a massive city-ship capable of space travel. They built many city-ships, but most were destroyed during the war with the Wraith. Their technology also appeared more advanced, being made of metal, digitalized, like the symbols on the Stargates, and utilizing crystals in their consoles instead of stone tablets. They also kept their archives in computers instead of downloading it into a person's mind.

Known Lantean outposts

 * Dagan
 * Doranda outpost (Destroyed)
 * Lantea Atlantus (Moved to M35-117)
 * Taranis outpost (Destroyed)

Mortal

 * Adalyx
 * Atlas
 * Brallymynn
 * Cynrrid
 * Dalera
 * Didthura
 * Dosa
 * Ea
 * Frodren
 * Glendolph
 * Helia
 * Hippaforalkus
 * Janus
 * Laphrotia
 * Llewcygad
 * Llyggabrd
 * Luthan
 * Melia
 * Minawara
 * Selmonkiv
 * Sigrid
 * Smylkamen
 * Srenala
 * Trebal
 * Tristac
 * Tsiggnayl
 * Vortensis
 * Wendamin

Ascended

 * Chaya Sar
 * Ganos Lal/Morgan le Fay (Presumed destroyed)
 * Moros/Merlin/Myrddin (De-Ascended)