The great dragon was a Safeholdian carnivore, smaller than the common dragon.
It was the largest and most dangerous land carnivore on the planet, filling the highest niche of the land-based food chain. It wast actually unrelated to the other Safeholdian species called "dragon", like hill dragons or jungle dragons, despite some superficial physical resemblances. In fact, it was more of a scaled-up slash lizard. (OAR)
The carnivorous great dragon was a Safeholdian predator that could pull down an adult hill dragons all by itself. (MTAT)