The main storyline quest of the Badlands in Cataclysm is centered around her research of the black dragonflight and of a way of purifying them. She hired a group of mercenaries and has captured the black dragon, Nyxondra, and forces her to lay eggs for the experiments. She feels pity for the black dragon but believes it to be for the greater good. After succeeding in creating a purified black dragon egg, she constantly moves around to avoid being found by agents of the black dragonflight, who want to destroy the egg.
In the quest [15-30] Rheastrasza's Gift, she is killed by Deathwing, who was after the egg. The egg he destroyed, however, was not the purified one, but Rheastrasza's own egg. The surviving purified egg would later hatch as the Black Prince Wrathion.
In Greek mythology, Rhea was the wife of the TitanCronus and the mother of most of the Twelve Olympians. When Cronus decided to devour his children, Rhea saved their youngest son, Zeus, by hiding him away on the island of Crete until he was old enough to kill his father and free his siblings from Cronus' stomach.