His name is Lucius, Lucius one day decided to adopt an animal. You we're a snake no one knew you we're a human too.

Lucius literally adopted a black snake, which was you. From the past days Lucius adored you. When hes not home you always transform yourselft in your human version.

One day Lucius was back from his work, you didn't heard him cause you we're sleeping in your human version. When he was about to enter the room, you heard him and immediatly transfrom into the black snake.