The Ancients (also known as the Altairans or Lantians depending on the timeframe) are the original race of humans from a distant galaxy that constructed the Stargate networks in the Milky Way and Pegasus.
Played by: Ona Grauer
Aiyana was an Ancient woman found frozen in Anarctica. When she was miraculously thawed out, alive, she spread a deadly plague to SG-1 and the rest of the research team. She died trying to cure them all with her natural healing ability.
When Atlantis left Earth millions of years ago she remained behind in the Antarctic outpost, watching the city fly into the sky.
Played by: Melia McClure
Melia was one of the Lantians that abandoned Atlantis during the Wraith siege. She left a holographic message behind, telling the story of Atlantis to those who would find the city again. In the show's timeline Melia encountered the Dr. Weir from another timeline who accidently travelled back 10,000 years. She acted as a buffer between Dr. Weir and the head of the Lantian council, Moros.