In 2373, the Federation Grand Jury was convened on this world to hear a case concerning the Orion Syndicate. Quark was a witness in the case and was called to Inferna Prime to testify, but the Syndicate attempted to have him killed en route. (DS9: "The Ascent")
Background information Edit
This planet was only mentioned in dialogue.
"in-FER-nuh" was the pronunciation for this planet's name from the script pronunciation guide. 
According to Star Trek: Star Charts ("United Federation of Planets I") and Stellar Cartography: The Starfleet Reference Library ("Federation Historical Highlights, 2161-2385"), the Inferna (Zeta Herculis) system was located in the Alpha Quadrant. This quadrinary star system consisted of a pair of G-class stars, a F-class star, and a K-class star. In 2378, Inferna Prime was listed as a Federation member.