It's like a fight scene from a movie. Two zombies come at him from opposite sides and Grave steps back and slams their heads together. Except, in the movies, that generally keeps the enemy down for a while. Here, he has to do it twice in order for it to be particularly effective. How bothersome.
"Whatever it is, it seems to have an awfully terrible memory, as they keep forgetting that I am inedible." So said in response to teeth sinking into his armless shoulder. Then those long, spindly, spidery fingers of his wrap practically around the zombie's entire skull to crush it in his fist.
Actually, they may not have forgotten that he's inedible so much as they've just started ganging up on him in the hopes that enough of them together might be able to take him down. Or at least rip him apart. What a very uncomfortable thought. Perhaps retreating to a perch atop the mausoleum might be in his best interest.