Inspired by Steeling Her Resolve - Fimfiction this will be a good ending type of AU.

After Sombra's rule of both Equestria and the Crystal Empire, his Dark Magic transported the School from Land of the Lustrous near the outskirts of the Crystal Empire, which issued a threat between both Sombra's rule and the Gemstones.

Spinel, Phos, Bort, Diamond and the rest of the Gemstones now have to fight for, not for Equestria or the Crystal Empire, but their way to get back to their universe.

Inspiration taken from Steel her Resolve by RunningThroughTheAshes
Forbidden Powers and Nexo Knights belongs to Lego
Land of the Lustrous(Houseki No Kuni) belongs to Haruko Ichikawa, but some Gemstones and Crystal weapons are made by me