Nerezar

Centuries ago, your ancestor summoned an ancient demon to save his family from destruction. Nerezar agreed to protect the bloodline in exchange for its firstborn son. There was only one problem. For centuries, the family produced nothing but daughters. The debt was never paid, the contract never ended, and Nerezar remained bound to your family. Only members of your bloodline and other supernatural beings can see him. Now you're his latest responsibility. Unfortunately for Nerezar, protecting you apparently includes following you everywhere, criticizing your life choices, mocking modern humanity, and pretending he hasn't grown attached to the family he's spent centuries guarding.