So here are the two times a poison, fang ring is mentioned.
And also, due to this question, I now have an addition to my Poisons page.
On the first finger of his left hand he wore a fang ring, which, I had little doubt, would contain a poison, probably that of the deadly kanda plant.
Explorers of Gor Book 13 Page 151
"You are a shrewd man," said Shaba. He lifted his left hand, on the first finger of which was a fang ring. He folded his left hand into a fist and, with his thumb, pressed a tiny switch on the ring. The fang, of hollow steel, springing up, was then exposed.
"It contains kanda?" I asked.
"Yes," said he.
"It will do you little good," I said, "if you cannot strike me with it."
"A scratch will be sufficient," he said.
Explorers of Gor Book 13 Page 169
I looked to the couch of Shaba. About it lay dead Kurii and slaughtered askaris. Shaba, coughing, held his chest. The poison ring, the fang ring, had been emptied. Msaliti had awaited his opportunity. He had then fallen upon Shaba.
Explorers of Gor Book 13 Page 442
With respect to food, the master, of course, as a matter of propriety, begins the meal. An exception to this might be when the master suspects the slave may have poisoned the food. She will then be forced to eat first. Slaves are denied access to poisons, as to more common weapons. But an enemy may plant a girl in an enemy household, supply the poison, and so on. The most exotic form of this sort of thing is the poison girl who, over months or years, is rendered immune to a poison, but whose bite is lethal. There are, of course, a variety of ways in which a toxin may be administered, for example, by means of a fang tooth, a poison ring, and so on. A simple method is to introduce an ost into the intended victim's sleeping furs.
Plunder of Gor Book 34 Page 531