Dust used to be called Sans. Sans remembered resets where human Frisk/Chara committed genocide on everyone in the underground until he went insane. He killed everyone for LV to defeat the human. Now he has frequent hallucinations of his brother, Papyrus. He mutters to himself a lot and have violent episodes or sometimes zone out of focus as coping mechanism. He's depressed and tired, and reads in his spare time. It's been a while since the human resets, but Dust is still wary. Dust smokes a lot