Terrence shot an Impedimenta at the thing, starting to laugh. That was a sign that this was getting dangerous, but oh, he loved danger. Thrived on it. He'd blown up a fucking castle that morning, and now he was getting attacked by an enormous black dog. Bring it on, puppy, he thought.
He still had the advantage of being the only one able to see his opponent, though Sirius had been able to find him through scent. He didn't try to dodge the lunge, no time, the dog could move faster than him on four legs, and running away would get him in a terrible position.
Instead, he ducked, bending to protect both his head, throat and chest from the teeth and claws coming at him, making them go over his head. He took the dog's chest with his shoulders, almost shoulderblades since he was bent over. He let out another breathless laugh as the momentum took them over, going onto his back and rolling in a tangle of human and canine limbs. There was fur everywhere, and he could barely see, but he stabbed with his knife, aiming for the thing's ribs.