The Highland Ravager is the third dragon in Emprise Du Lion, and I believe it's the strongest in the game. It doesn't help that he's immune to fire, which happens to be my go-to element.
Even with my entire party decked out in masterwork armor, high-level weapons and dragon slaying runes this dragon destroyed me. In case you're wondering, my Inquisitor is level 21.
I'll try again later... much later.