Ava is a malevolent and sadistic dark spirit who inhabits the body of the protagonist. Ava's goals are entirely self-centered, with her only desires being self-preservation and the obtainment of greater power. She guides the protagonist down the path of a destructor. To reach this end, she grants him power along the way to ensure both of their success. Their relationship is of, reluctantly, mutual benefit. 

Ava's voice actress should be able to craft a unique and almost squirrelly tone. Think of more mischievous than abject evil, but still capable of conveying sinister tones when necessary. Think of the English dub for Migi from Parasyte, or more aptly, Cirrus from Honkai: Star Rail. Feel free to include versions of your audition lines with voice effects if you so choose, though try to keep some takes with your normal voice. Ava's voice in the series will have some form of vocal effect, so if you think you can master the proper one, go right ahead!