Mass shadow/Legends

A mass shadow is a type of stellar anomaly which prevents hyperspace jumps, and can pull a ship out of hyperspace, should it venture too close. Mass shadows can occur naturally, caused by gravity wells such as a planet or gas giant. There is one known case of an artificial mass shadow, created by Republic Leiutenant Bao-Dur on the planet Malachor V during the Mandalorian Wars under the Jedi general known as the "Jedi Exile." Temporary gravity wells can be created by such ships as the Interdictor-class Cruiser of the Old Republic, and the Interdictor Star Destroyer of the Galactic Empire. However, it is unknown if such occurences can be considered a true mass shadow.

Star Wars Knights of the Old Republic 2: The Sith Lords