I just came up with an au idea
It’s basically where the monsters were never sealed underground and the war is still on going
I’m callin it DistopianTale,
because of the war the world is in like a distopian state.
In this au the war started because Asriel was killed, similarly to how he did in undertale.
Now any human who finds themselves on the mountain, will be killed and their soul will be used to make monsters stronger
Monsters have adapted to be more physical ig, like they can bleed and stuff and they don’t immediately dust after they die.
It’s harder for humans to get monster souls because unless their soul is that of a boss monsters, it will almost immediately shatter when the monsters dies.
So anyway, Frisk find themselves in the mountain, like normal, and Toriel find them. Now she almost kills them but Frisk has no EXP (which boss and half boss monsters can see easily) and they look so much like Chara that she just can’t. So she warns them, and tells them that she will have to kill them if they meet again, and leaves.
That’s really all I got for now but we’ll see if I come up with more later