It was another Genocide run - Frisk fighting Sans in the Judgement Hall, ending in Frisk landing the killing blow. However, instead of dying from the last blow, Sans absorbed the six Human Souls he had kept with him in order to remain alive; after this, the parts that were fading to dust were hidden by a rainbow flame (shown in the image of Color! Sans on the right). Upon absorbing the Souls, Sans used his newfound powers to end Frisk's life - only for the world to RESET afterwards.