Abandoning Princess Celestia, Sunset Shimmer flees through the mirror, to prove her mentor wrong.

But the world she finds herself in is nothing like what she thought it would be. Humanity is being eradicated by souless machines. In numbers that makes even Sunset's stomach churn.

Machines called mobile armors.

Forced to join the war, to protect the few she now calls friends, and for a chance to return to Equestria at all, Sunset is offered the chance to pilot one of mankind's last hopes for survival.

They call them Gundams, and Sunset has been chosen to pilot the Gundam Barbatos.