After the battle of Yavin and the destruction of the Death Star, the Rebels proved that they were a serious threat to the Empire. The Empire forced to take that threat seriously, responded with new technology and weapons such as the Dark Trooper project and the TIE Phantom. The TIE Phantom research, under the direction of Admiral Sarn, was conducted in the Dreighton Nebula. The Nebula, the site of a major battle in the Old Republic was rumored to be haunted and the source of ships mysteriously disappearing. This provided perfect cover for development of a top secret stealth starfighter.
After Admiral Zaarin's attempt to cloak a Corellian Corvette in his Vorknkx project, all efforts were submitted to the cloaking of small starfighter craft. He was able to modify a B83 assault fighter with a cloaking device. The code name for this craft became the Phantom TIE fighter.
The TIE Phantom packs slightly above normal firepower for a starfighter of it's class. However the main improvement of the ship was a cloaking device. With the stealth shield in place, short and long range delectability of the ship was almost nonexistent. Should the Phantom have gone into wide production, the Empire would certainly have had the upper hand.
Prototypes were tested near the planet Dreighton. When preliminary tests were completed, Lord Vader took control of the project and ordered the full scale production of the Phantom. Sigma Squadron, the first wave of these deadly TIE fighters, came within mere hours of launch before the construction facility on Imdaar Alpha was destroyed, along with the Empire's stockpile of the ship. Admiral Zaarin's command ship, the Super Star Destroyer Terror was also eliminated along with the base. The admiral was retired from active duty personally by Lord Vader and the project has not been restarted. The Rebel strike team, commanded by Ru Murleen captured one of the precious vessels, but the fighter was destroyed at a rebel base due to Imperial security fail-safe measures.
But the blue prints for the phantom fighter are still on Coruscant and are available for members of the Emperor's Inner Circle.