The bestial, reverberating filled roar that shook the entire cavern continued on for many long, anticipatory seconds as the Fiend announced its presence, something that allowed us to begin painting a picture of what this Fiend might just be like, albeit a picture that had many different routes it could take.
That roar could be an announcement to allow us to get prepared, a challenge that it was levying unto us and giving us forewarning of its intent to come and fight us, or it could be the mere wordless, mindless roar of an animal that craved nothing but violence and death for the sake of slaking its thirst for blood and flesh.
Sophisticated and honor bound, perhaps this Fiend was a warrior wanting to challenge us to a battle, to test its might against ours in a battle to the death where one side would come out on top, stronger and more experienced than before.