Yin is an evil character in this series, who has killed thousands of angels for their halos, each making her note powerful. When she was banished from heaven however she lost her physical form and took Remi as a vessel. Now, whenever yin gains control over Remi’s body, there is absolute havoc in the underground. Yin is  by definition evil, and manipulative. Her voice is fairly low/normal. So basically that’s all there is you would maybe need to know about her. Do be aware as the series progresses though, yin will begin saying a few disturbing things. So if you do not want to say anything like that then this role is not for you