|Out of universe information|
Thirty million years ago, she was left on the island Santorini was Atlantis building site. She was placed in a stasis pod when the rest of her people left Earth in Atlantis. Thousands of years later, you will find three Trust agents on her Santorini the original site of the City-ship by Atlantis. They used Cassandra Fraiser to open her pod. (SG1: "Transitions")
When she was released from the pod of about ten thousand years after that, she used amplifier bracelet to create an energy blast that took out the three Tau'ri members of the Trust who had opened her pod. Cassandra Fraiser, which had been captured by the group, was able to defend himself from the explosion to use her own powers.
Amara would later use amplifiers bracelet to create a wormhole from Stargate Command for Atlantis so for her to go to the city to cure Ancient contagion, running amok. Shortly before his death gave Amara bracelet to John Sheppard with the task of submitting it to Cassandra. (SG1: "Transitions")