This story is based on what would happen if Chara managed to win in the Undertale trilogy, if Sans kept on attacking and caused everyone to be destroyed by his energy, if he was ripped apart from his determination and hatred.
This answers the question with a split story that is set in the Underfell universe. Frisk has 5 days to make it back to the barrier otherwise Chara will kill her without warning. If she succeeds into getting there she may challenge her again. But in a universe where everyone is much more aggressive than normal. Who can help her at all...? Well that's down to a Flower, a Spirit, and a Skeleton to decide...