In those days, we commonly transmuted metals and other wonders, but the King was most interested in our mastery of the Substance, which those not of our order dub "wild-fire."
A slight misnomer. To the uninitiated, the Substance indeed seems uncontrollable. Water will not extinguish it, nor plate of steel, repel it.
Our order alone knows its secrets. In bare stone cells beneath the Guildhall, our acolytes prepare the Substance with utmost care and ancient magic. Apprentices then remove the jars to a secure storage. Overseeing its purity are the Wisdoms such as myself, who are adept in the alchemical mysteries.
Should an acolyte prove unworthy and allow the Substance to ignite, the ceilings are spelled to collapse and fill the room with sand. For once lit, only smothering or starvation will quench the fire.
Many years did the Alchemists' Guild served the Targaryens faithfully, until we were beset on all sides by the envious.
The Order of Maesters, who dismissed all learning except their own and the charlatans who hawked green paint, and worse, in our names.
After the unfortunate Prince Aerion Targaryen, drunk with wine, boasted that a draft of the Substance would transmute him into a dragon, we lost our royal favor.
Then came the wise King Aerys, Second of His Name. I was merely an acolyte when he restored our Guild to its former glory. As had his great forefathers, he appreciated our secret arts, even naming Wisdom Rossart as Hand of the King. Together, they punished his enemies as befits a true Targaryen.
But, sadly, King's Landing must have fallen before it could be used, and many of our Wisdoms disappeared in the sack of the city. Victims of ignorance and envy as ever, I'd wager.
Yet our order perseveres, Like the Substance, which grows ever more potent as it ages, we perfect our ancient arts in darkness, forgotten by the world. We are masters of the fire but live only to serve.