Jon didn't even bother using magic; it would be too quick and far less satisfying. Killing someone with your own two hands was far more personal and close, somewhat soothing his seething rage, so he took his sweet time butchering through the Unsullied as he ploughed through the hallways. Truthfully, he could have found Illyrio Mopatis instantly and killed him and only him, but that would be too easy. Everyone remotely associated with the fools who dared order his family's death would perish as a warning.