Theriac was more of a concept than a single recipe. It was a cure-what-ails-you brew with multiple ideas of remedies. Its focus was on counteracting poison, but “poison” was as loose an idea as “toxin” is in alternative medicine today. Maybe you actually ingested poison or were bitten by something venomous, or maybe you received an elf-shot or breathed bad air. Poison could be thought of not as a class of harmful chemicals but as an agent of sickness, however it was received.
Theriac began with the flesh of a poisonous serpent, on the grounds that the snake could neutralize its venom. One of the top magic principles was that like cures like, so the creature that delivered poison could also cure it. It might well also include a dried scorpion, another famous poison delivery system.
From there, the list of ingredients varied. In past essays (last August) I talked about various herbs; their herb-lore was extensive, if sketchy. Some herbs absolutely had an therapeutic effect, while others perhaps just resembled a body part or followed some other magical-logical link. Honey, spices, nut oils, and even brewer’s yeast might go into the theriac next. It’s likely that wine was the liquid element. Individual methods would dictate which herbs and liquids were cooked before it was considered properly mixed.
The key to theriac was its uniquely long aging process. Theriac sat, probably corked, for at least a year. Judging by other brews that aged for three to nine days, it was probably strained at the end to remove the sludge and pieces, and the resulting liquid was stored in a fresh bottle.
After that, theriac was the ultimate cure-all for anything poison might have caused: actual venomous bites, infection, migraine, or epidemic. It was probably employed for cancer, too. Adults could drink a little bit of it (probably mixed into wine or ale). But theriac was considered too strong for children. A sick child was treated only by rubbing it onto the skin.