In the mirror universe, the Pentalla Nebula was a stellar object, a nebula located in the galaxy's Alpha or Beta Quadrant. In the visible spectrum, the nebula appeared as blue and purple waves. (TOS - Mirror Images comic: "Issue 2")
In the year 2264, the Imperial Starfleet ship ISS Enterprise attended an off-the-records rendesvouz with Juraav's Orion trading vessel. Captain Christopher Pike traded phasers and phaser rifles from the ship's complement for Juraav's dilithium crystals. Offended by a hidden stash of Bolian brew, Commander James T. Kirk and Lieutenant Hikaru Sulu allowed Juraav to keep the phasers when the Orion trader retrieved the brew, and left three Orion slaves behind.