Rose and the others is an au of Undertale the au is Twisttale search up Undertale gaster and see what gaster did basically rose is an au of gaster.

Me: look up what bad things did gaster do and see
But I'll tell you what I know
She messed up rivers face
She messed up Tjevil
She uh killed humans I think
All I know is that she did verrrrry bad things in the past

What happened?