Ashton was born and raised within the Shadowfell, and it has left its mark on him. He fends for himself, doesn't put his trust in others. It is curiosity more than anything that makes him approach Caslte Nowhere; surprised by the fact there seems to be a small gathering of wolves there now, when most simply prefer the safety of solitude.
He doesn't really join the pack. But every now and then during his travels, he stops by the castle, and informs Kajin of what is going on in the area. Does he always speak the truth? Who knows.
