An Athanor, also known as a Tower Furnace, is a tall, slow-burning, self-feeding furnace used in alchemy. Once filled with coal, it can run for a very long time without any human supervision, allowing the alchemist to perform long-term experiments that involve heating a substance to a constant temperature for an extended duration.
Exactly how an Athanor works is a little unclear. There's a drawing available at wikipedia, which suggests it has three parts that open, a top lid and two side-doors. Inside appears to be some sort of mechanism, possibly for controlling temperature or fuel consumption. The specifics of construction or mechanism may well be encoded in a metaphor in Philostratus' Life of Apollonius:
Athanor is an occult hill surrounded by mist except on the southern side, which is clear. It has a well, which is four paces in breadth, from which an azure vapor ascends, which is drawn up by the warm sun. The bottom of the well is covered with red arsenic. Near it is a basin filled with fire from which rises a livid flame, odorless and smokeless, and never higher or lower than the edge of the basin. Also there are two black stone reservoirs, in one of which the wind is kept, and in the other the rain. In extreme drought the rain cistern is opened and clouds escape, which water the whole country.
Game and Story Use
- Athanor's are specifically intended to run unattended. An character who is secretly an alchemist can still carry on a social life, and put up a front while keeping their secret identity hidden. If their experiments are mostly long-term ones, they'll only have to check in on the lab from time to time.
- Of course, this opens the door to all sorts of things going wrong if the plot demands it. An athanor might start a fire, release poison gas, unleash wild magic, or cause other sorts of trouble while the Alchemist is away. Which means saving the city (or picking up the pieces) is left to the player characters.
- In a high fantasy setting, the function of an Athanor might range from complicated steampunk machinery employing more-or-less normal science, all the way out to a conjured and bound Fire Elemental. Odds are good that the wizard or alchemist will have a custom-built athanor, probably with some magical wards on it, or magic properties of its own.
- What exactly that coded myth by Philostratus means is probably up to the GM to decide, but it could easily be instructions on the proper shape and composition of such a furnace. Or it could have directions for a specific alchemical recipe or experiment that uses an athanor. You could even consider it a blueprint or feng shui diagram for how to properly set-up and arrange an alchemists lab.
- Even if it's a coded myth, it could also be a description of a lost ruin.
- If you want your constructs to be different, you can have a steam-powered clockwork statue running off one of these.