"In order to kill a demon, a demon can only kill a demon, or something stronger than a demon in the three kindoms. A human can't harm a demon nor angel unless a angel feather is equipped or attached on a weapon to harm a demon. To harm an angel a human must drink demon blood to become something more than human..."

The rules in my comics and how I see things! but this is the part where RED09 angel form gives the angel feather to Anya as a child, he tried to save her from a horde of demons as he watcher her family get slaughtered, now upon his defeat his last moments he gives her one of his angel feathers so she may survive tracking the demons that killed her family. Getting to the underworld wont be as easy as Dante's inferno...