Famous, one might even say, notorious beverage created in the Gladsome Antglade.
The precise recipe for the drink is a closely held secret. However, the effects of drinking a bottle of Persoc-Itoome are that the consumer suddenly acquires a burst of what is referred to as "Persockity Vitality," something of a state of hyper-activity.
It became quite popular toward the end of the so-called Dull Ages, until herbalists in the reign of King Adler Sartoriusson studied the drink's effects on consumers, and noted its deleterious effects. Persoc-Itoome was thus banned in the Mephitist Empire, and the familiar black-and-yellow magick coolers vanished from open site. (As noted in "Speaking Volumes," however, a certain underground trade in the beverage continued to flourish, at least until the time of that adventure, late in King Adler's reign.)
Persoc-Itoome continued to be manufactured in Gladsome Antglade at the time of The Ballad of Adler Young; a cooler is spotted next to Catherine O'Daises' HQ, and King Estmere finds (and consumes) a bottle, which gave him the strength (and Persockety Vitality) to rescue a Floozie in distress. The firm is run by one of the son-cousins of the Duchess O'Daises, Matholwch.
It is believed that the beverage was also produced, without license, in Vulpitania, in keeping with that realm's habit of producing knock-off goods.