He is the god of rebirth(the white one) in the drama, but later becomes the god of destruction(the black one). The drama doesn't explain why he changed. I've read the script writer has some story in mind, but it was cut out in the end. I want to know it so much!
The white one only appears for several seconds
, but there are a few shots for him in the show's opening. It's my favourite opening in the series. [link]