Eris was the servant of Rezo the Red Priest and later, Copy Rezo. From a young age, she served as Rezo's assistant and apprentice, helping him perform his miracles. She also assisted in his reserch to cure his blindness. It is implied that she may have been in love with Rezo as she is seen to be broken hearted over his failure to cure his blindness.
After the death of the original Rezo, she hired the swordsman Zangulus and the sorcerer Vrumugun to hunt down Lina Inverse and Gourry Gabriev and bring them to Sairaag, as well as released several wanted posters of the two on the orders of Copy Rezo. She is also the person responsible for cloning Vrumugun. Eris is killed in cold blood by Copy Rezo after he merged with the ancient demon the Demon Beast Zanaffar, buried in the Holy Tree Flaggoon.