Optimus Prime ends up arriving in Equestria during his travels after Age of Extinction. And finds out that the ponies who live there are more than meets the eye.
What would happen, if Nightmare won during that first confrontation, and was actually a decent mare to begin with? This is what happened in that alternate universe!
a Star wars X MLP Crossover!!! Nightmare has created her own faction and is rebelling against Celestia! Luna is nowhere to be found, and to top it off, Nightmare's side has an advantage. Follow Zero 'Red' Star and the NLR as they fight against the SE