The Dreighton Triangle was a region of space within the Dreighton Nebula.
Following the Battle of Dreighton and massive fighting in the Dreighton Nebula in general during the Clone Wars (which led to the mutual annihilation of both Republic and Separatist forces deployed there), stories about ghost ships and hauntings by the spirits of dead pilots began to spread among the general populace. Many believed that a ship entering the Dreighton Triangle would never be seen again.
Subsequently, the superstitious tended to avoid the area, especially fearing the triangle formed by Aeten II, Dreighton, and Imdaar.
This reputation in the general populace made the region the perfect cover for the Galactic Empire's Phantom TIE project in 3 ABY.