The Everfree was unnatural. But even though there was vicious monsters, they can be easily pacified. But those things are nothing compared to the ones made in metal.
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.
Receiving a Megatron costume for his birthday got Denis into a fit of glee. Waking up in strange land as 'Lord Megatron' got him into a fit of confusion. Thinking it was a dream, eased his mind; only if it were so.
When a group of archaeologists uncover a metal being encased in ice beneath the white wasteland of the Frozen North. They unintentionally awaken it. It's purpose?.. To bring death to those who disrupted it's mission.
When an ancient relic cappable of untold power lands in the magical world of Equestria, two universes will come together to claim this relic. Though some want it for evil purposes, some want it far away from evil-doers for the sake of peace.