Frisk are a subspecies of human known to create abnormal amounts of Determination just by existing. Unlike their counterpart, the Chara, they are more often than not unaffected by the inherently evil properties of the power source. In fact, they are driven by an unhealthy desire to spare everyone, even at the cost of their own life. They have no specific gender and, like mimics, have to assign themselves a gender. This leads to the biological alteration of receiving genitalia to match their assumed gender. Nothing can explain their obsessive attraction to being a pacifist.