The Abbess is the leader of The Valleysmen people, including Zachry and his family. Her name comes from a ruined abbey nearby that survives from before a nuclear holocaust called the Fall. The Abbess preaches the value of civilization, encouraging the Valleysmen to try to act the way people did before the Fall, but so much knowledge vanished during the Fall that the Abbess and the other Valleysmen often don’t understand the purpose of the relics that survive from the old civilization. This abbess probably isn’t the same person as the Abbess of the Mountain Colonists from “An Orison of Sonmi~451,” who is already in her 60s in that pre-Fall story, but it’s possible that she is a reincarnation of that Abbess, given that role that reincarnation seems to play with the comet birthmark characters.