Read Into the Shadow by 08raven71 first!! Nico is stuck being something he never wanted to be a Hero. Just because he is forced to be in this situation - forced being used very broadly since he get paid per save- it doesn't mean he will be nice to anyone. Nice being the opposite of his existence... And demi-God happenings are keeping him distracted a lot. don't forget about his three headed dog.
14 parts