Plot summary
Dr. Elizabeth Weir returns to Atlantis in the form of a "digitally ascended" being, who hopes to use Atlantis to construct human bodies for her consciousness and for those of eight other Replicators who likewise hope to Ascend. Weir convinces the team to allow the other Replicators to rebuild their bodies after she summons them once she rebuilds her own as FRAN, the Replicator McKay had previously created in order for them to build themselves human bodies to live in. However, one of the Replicators, Koracen, doesn't like it and escapes the lab in order to remain a Replicator and seek Ascension. When he tries to kill Sheppard, Weir destroys him and realizing that she and the other Replicators are too much of a threat, sacrifices herself to trick the other Replicators through a Spacegate where they are frozen forever by the cold of space and deactivated.
Credits
Adapted from Wikipedia contributors, Stargate Atlantis season 5. HTML formatting and reference markers removed.