Melody of Vengeance

In the past, a very kind woman in City X was killed due to envy by someone she loved so dearly. Thus, she was summoned by angels so they can lend her a precious asset. As a compensation, one of her descendant shall inherit a bad life in order to let Vengeance do whatever it wants freely and ending it with a very unique melody. However, was there a catch in this written prophecy?