When possessing a mob, some artifacts simply don't work. This includes, but is not limited to, the Fire Gauntlet, Power Glove, Pocket Piston, and all the Pendants.

Hmm. Do you happen to know whether there's any artifacts that do work?

Ladysnake/Requiem#326 <-- See here for the issue posted there.
Invisibility Scarf works.

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