Board Thread:General Discussion/@comment-6192846-20150326001739/@comment-6192846-20150401211300

Octo put it plainly. The SCP story confirms contractors can be killed by other contractors and/or vessels of sin. The important thing is the demon's power supplying the healing and power contractors possess. As I pointed out earlier, a similar mechanic occurs when Gretel uses Banica's power to cancel out the Demon of Greed's in Praefacio.

The demon's vessel being involved seems to just be coincidental. Neither Crim nor Carlos were contract to the demon, the latter just happening to have some of the magic-infused vessel in dust form when he used it on Banica.

The vessel of wrath is convenient in that it seems to be a magical poison by itself (referenced in Lunacy song and again in EFEC novel with Carlos' poisoned soup). The demon's magic is definitely geared toward the express purpose of killing individuals, including contractors, but the only time possession was involved in the murder of a contractor was with Clarith and Nemesis, both of whom just happened to have contractors (or former contractors) be the object of their wrath.

We'll have to see how this works with Gumillia (who now carries the key) and Lemy who remains contracted to Banica via Gretel.