The Age of Iron.

Unicorns have their magic to protect them. But what does that leave the Earth Ponies with? Something much stronger...

When the world was young... When Equestria was nothing but an idea... When magic ruled as the sovereign power over earth and sky without equal... Therein was the hot weathering of mettle... And of metal. The very birth of Earth ponies greatest and most prideful discovery upon the elements of nature: Earth.

One-shot POV.