An athanor is a high-temperature furnace, specifically designed to heat alchemical vessels at constant temperatures for long periods. It is therefore frequently shown with a flask (such as a retort) atop it, which fact is always blazoned. (Without the flask, the athanor is indistinguishable from a tower.)
Though a period artifact, we have no examples of the athanor in period heraldry; the illustration is from a 1545 translation of the writings of Geber [Singer 739]. For related charges, see oven.
The Order of the Athanor, of Meridies, bears: A retort atop an athanor argent.
Luu Naran bears: Sable, a retort atop an athanor, in sinister chief a cross moline, a bordure Or.