Haven't returned

When Gregory got to the scene, Clara has left already.

He only saw the dead wolf and his expression darkened immediately, his eyes started glowing red with anger. 

He has taken a likeness to the dead demon, as he was like a friend and a brother to him, he has lost a lot of his turned demon, yet this one has survived with him for centuries. 

He is the one that was helping him monitor Sonya as well. He gave him the easy tasks but he stubbornly gave himself the hardest.

He knew if Clara was well good with her abilities like her mother who killed hundreds of his demons, with the same abilities Clara posses now, she wouldn't even give him the chance to turn into a wolf before getting rid of him.

And now, he just made Clara know how valuable the air element ability is. When Clara's mom used it on him and his army then, thanks to the scientist who was at the scene then, he has used them as a sacrifice to remain safe.