Vengeance got to his au with Dust Sans since it was to protect against Nightmare and the rest of his followers* Dust then proceeded to ask a question that triggered a lot of emotions* so . . . Vengeance what's your story? since I've told ya mine. well I was initially Classic Sans and then I became what you are and after a pacifist rebellion route in Dusttale I broke free from the murderous cycle that I was in. Dust looked surprised* huh . . . well that's definitely interesting. and well I am somewhat weak in HP Dust. How's that? well since being part Classic Sans and part of you I can get beaten easily but if I choose to go mad I can revert back to my mad, insane Dust Sans self. anyway it's not an easy subject to talk about.
