I’m doing some more research, this time on a condition known as Phossy Jaw (description of symptoms below are taken from the Wikipedia article here):
Phossy jaw, formally phosphorus necrosis of the jaw, is an occupational disease of those who work with white phosphorus, also known as yellow phosphorus, without proper safeguards. It was most commonly seen in workers in the match industry in the 19th and early 20th century. Modern occupational hygiene practices have eliminated the working conditions which caused this disease.
So if we assume our antagonist has Phossy Jaw (noted by our brilliant detective Portia Adams) and it was caused by handling white phosphorous, then we now need something that expels a great amount of oxygen for it to interact with.
I’ve got a question out there on Quora right now, trying to see if this is feasible.