Chara woke up, not in their room, but on a bed of golden flowers down in the Pit. There's a human child sitting next to them, so this obviously could only mean one thing: Human invasion. So, they'll just murder the child, go home and make sure mum, dad, and Asriel are all okay. It's not like they woke up years in the future where they've been dead the whole time, right? [Charisk]

A Fury Unleashed. A crossover AU of Undertale and FURI, where the Underground is a prison and the monsters are the jailors or "guardians" keeping "Frisk" locked away for the safety of the world. The AU is a genocide run.

NOW COMPLETE! - In which Frisk lives in the Ruins forever and runs a restaurant. Sans moves in to help build some new infrastructure. Frisk is... a perfect child who can do no wrong! And Sans, he's so good at protecting her... that he could do it in his sleep.

Chara awakens in a field of flowers deep in the Ruins. Weren't they supposed to be dead? Instead they form a tenuous alliance with a human invader, promising to help them through the Underground if they will shatter the barrier. So begins a tale of an unlikely partnership and an even unlikelier friendship. (Bonus! Annotations chapter after the story!)