The Harbinger who has always been two-sided, He could be Nice and warming yet something deep inside his abyss heart he's always been, Childe's personality drastically changed. Although he appears

His appearance; tall male model. He has short ginger hair and dull blue eyes. He wears a red Fatui mask pulled off to the left side of his head, and a beaded earring with a red crystal.

His vampire side came with becoming a fatui harbinger 

A sly fox like personality, Almost sadistic yet two faced.