Over 100 years ago, during Avalice's oldest and deadliest war, Merga was bioengineered to be the perfect warrior, making her ruthless and power hungry as she fought in said war. As a result of her possible warmongering, Merga was sealed in crystal prison that was locked by the Kingdom Stone's power, and hidden deep in the ocean off the coast of the Island Chain, Parusa.
100 years later, as a result of Lord Brevon's defeat, the Kingdom Stone is destroyed, destroying Merga's Crystal Prison as a consequence. Now freed from her imprisonment, she sets out to resurrect the ancient super-weapon, Bakunawa, to execute vengeance on the Avalicians and "Purify the World". She also holds a dark secret about the leaders of Avalice which will change the history of the Three Kingdoms forever and fracture the loyalties of her enemy's followers. To accomplish her goals, Merga hires Corazon Tea to transport her troops and supplies, and enlists the help of Aaa to build weapons and machines for her army. As far as she knows, Merga is the only Water Dragon in existence, as she is currently unaware of the existence of another Water Dragon in the present day.