I was thinking the killing would be by suffocation and heart-stoppage, basically. Poison would be a good option, I just hadn't considered it. The creature needs the muscles, or at least the skeleton, intact or it won't have anything to animate. They're not intelligent, they're primally driven - they're in a near-arctic environment, and once a body is obtained, they then use it only until they find a new, warm body to take over.
I'll check the Maleficant, I've got most of the RM2 Companions.
If I wanted to be particularly gruesome, now that you have me thinking, I would have it steal the nervous system from the brain down, and just take over the body. The victim would still have its mind and some senses, but the body is off-line, basically. Hmmm.