Flavie is an elite Rogue Scout who, at the time of the hero's arrival at the camp, is on guard in the area between the Blood Moor and the Cold Plains. Before completion of the Den of Evil quest, she advises you to stay in the Blood Moor. After completion of the quest, she warns you about the dangers ahead.
Flavie will attack any monsters close to her. She is not attackable and cannot die, so she is interesting to have around when fighting bosses (especially Uber Diablo).