Oh fuck yeah. Atem probably won't kill him, because he does still feel that killing monsters is Not The Answer, but 1. are you good with it being a human Atem's fond of and would demand imperiously for Gabe to let them go (I figure any attempt at telling a cat what to do will make gabe dig his claws in harder)? If so, he'll fuck Gabe up more severely, and 2. do you want him hit with the uh-oh regrettios spell?