Hyperspace

Hyperspace is a superluminal parallel dimension that makes galactic civilization possible. Long ago, ancient human and Duros cultures reverse engineered mysterious and pre-historical technology to create hyperspace cannons, hyperspace beacons, and, eventually, the modern hyperdrive. A trip that would take hundreds of thousands of years at sublight speeds takes only hours or days in hyperspace.
In these times, hyperspace travel is ubiquitous and taken for granted by most of the galaxy, but it is not without danger. Points in the alternate dimension have corresponding points in realspace, and objects with enough mass in realspace (such as stars and planets) cast mass shadows in hyperspace. A collision with one of these mass shadows usually spells doom for travelers. What’s worse, objects that are navigable in realspace can prove deadly obstacles in hyperspace. Even something as benign as a nebula can create an impenetrable mass shadow.
This is why established routes along well-explored areas of spaceare essential to intergalactic travel.