Max made an AU based on birthstones she called Gemtale
Sans is Peridot,Papyrus is emerald,
Frisk and Chara are ruby,
Undyne is sapphire,Alphys is topaz,
Asriel is diamond,Toriel is amethyst,
Asgore is garnet,Muffet is aquamarine, Grillby is pink tourmaline, Flowy is zircon, Gaster is pearl

Sans is the only one that can use different colored gems besides his own making him a target for Asgore's plan to defeat the humans.
Sans is head of the royal gard but doesn't hate humans he hates his job... his role and wants to be free like the fireflies he watches at night when no one is around!

Which AU Sans will save him from his grief?