Mirrorspace

Mirrorspace is a realm where strange energies roam in chaotic, multicolored patterns. No objects are native to mirrorspace, so it is empty of all matter. Locations within mirrorspace correspond to locations in realspace , but mirrorspace distances are variably compressed. This means if you were to travel at a certain speed for a certain amount of time as a journey in realspace, you will have traveled much further within mirrorspace over the same time and speed. As such, mirrorspace can be used to cross the vast distances between stars, using the conventional propulsion of ordinary starships.
While it is possible to breach the divide between realspace and mirrorspace, it is very difficult and takes a large amount of thaumatic energy to do so. Very few races in the galaxy have learned to do this, but of all the known allies, it is only the Amuran tribe of Men who have achieved the skill of mirrorspace navigation. Therefore, all interstellar traffic requires either an Amuran guild navigator or their proprietary hardware in order to enter or exit mirrorspace.

Distance Compression:

Compression within mirrorspace increases exponentially, with distance, away from gravitational sources. This means that realspace locations near a source of gravity, such as a star or planet or even large ships, will cause corresponding mirrorspace to be far less compressed, making travel within that area far slower.
The larger the source of gravity, the further out the effect will influence compression. A large star might reduce compression significantly up to several light-years away. Beyond the influence of all gravitational bodies, compression within mirrorspace can reach as high as 100 billion. Because of this, interstellar travel through the vast distances between stars is relatively swift, while travel close to stars, or especially within the planetary systems themselves, is far slower.
A good way to visualize distance compression within Mirrorspace is to observe the gradient of the Mandelbrot set. As you get closer to "attractors" in the set, the depth gradient compresses sharply. Far away from any parts of the set itself, the gradient is extremely shallow. If you consider your starship's speed to be a certain number of depth grades per minute, you can easily see how navigation becomes far more speedy out in the open, away from all the interesting things.

Currents:

A current flows within mirrorspace in the opposite direction of gravity. This means that while gravitational bodies within realspace will attract objects toward them, they will repel objects from their location within mirrorspace. This takes the form of currents, which can cause a ship to be swept away if not navigated with skill and care. The speed of the current will oscillate gently, making compensation more challenging than merely thrusting steadily against it.
The motion of a massive body in realspace will also create a doppler effect in its mirrorspace currents, with the leading edge of motion corresponding to tighter currents with stronger waves. The trailing edge of motion will have further reaching currents with weaker waves.

Turbulence:

When multiple gravitational sources are causing currents to overlap, they will create turbulence in the form of sympathetic resonance. This causes very complex patterns to emerge in certain regions of mirrorspace, which can be difficult to navigate through.
Because of the resonance patterns, often the turbulence is mild noise of little consequence. But in certain zones, where the waves harmonize, the result can rock ships about so severely that it is best to simply avoid those areas.

Explosive disruptions:

Explosive events in realspace can cause large current waves to travel outward within mirrorspace for some time until they finally fade away. The largest explosions, such as a supernova, can be so disruptive as to inhibit interstellar travel for weeks anywhere within a hundred light-years of the explosion.

Jump points:

In order to enter or exit mirrorspace, a rift vortex must first be generated. This can be achieved by large amounts of thaumatic energy being applied using specific complex coding which breaks down the barrier between realspace and mirrorspace. A one-way vortex then appears, its size dependant on the amount of energy applied.
When physically approaching the jump point vortex, a powerful gravitational current grabs hold of any object which has entered it, pulling it across the barrier to the other realm.
Jump points can be sustained by continuing to apply energy, but at a lesser rate than used for opening. If left alone, they will close naturally within a few seconds.

Etherium:

When objects native to realspace are traveling through mirrorspace, the local energies react with the material, causing a gradual crusty buildup of exotic particles to accumulate on its surface. For starships, the effect is much like that of frost on glass and can be noticed within an hour of mirrorspace travel. Sensors can begin having negative effects within six hours, and after a full day, most ships must exit mirrorspace or become fully blind until they do.
Upon returning to realspace, the etherium buildup rapidly evaporates, as the exotic particles are highly unstable outside of mirrorspace. It can take anywhere from seconds to a full minute to completely burn off etherium accumulated during a long journey. Once the etherium is gone, there are no lasting effects on any materials which were coated with it.

Navigation:

Successfully traveling through mirrorspace requires a skilled navigator using up-to-date gravity charts to plug into the ship’s autopilot for a specific route. Autopilot is possible only because for the most part, the gravitational landscape within mirrorspace is steady. Navigating any uncharted or unplanned route is going to require someone with the thaumatic skill to read the gravitational currents and match them up with star charts.
Because there are no visual points of reference within mirrorspace, it would be a near certainty that an unskilled pilot would get lost in the currents on all but the shortest trips. To assist with this, the Amuran tribe of Men has formed the Navigator's Guild, which supplies skilled navigators for interstellar travel of all purposes. This sect is highly insular, its navigators utterly loyal to the Guild. They have developed proprietary thaumatic technology that assists in the navigation of mirrorspace.
Long-distance navigation generally involves plotting routes which avoid the gravity wells of stellar bodies at a great distance. A straight route will quickly intersect with the currents of a star, even several light-years out, causing turbulence and currents as well as a severe reduction in distance compression. Therefore, the fastest routes by far are always curving around stars, keeping them at the maximum distance until the destination system has been reached.
Planetary system navigation is far more tricky, involving the precise charting of courses to avoid turbulent zones when possible. This is particularly important in treacherous areas where sympathetic resonance of currents have caused severe turbulence. As a ship’s destination draws near, the current waves from that planetary body become dominant, smoothing out the turbulence. Additionally, approaching a planetary body will stretch out distance compression to as low as ten when in the vicinity of near orbit.

Beacons:

One navigation aid created by the Guild is the mirrorspace beacon. A beacon is a small piece of hardware that sits in realspace and maintains a microscopic jump point into mirrorspace at all times. This is too small to physically affect anything, but it does allow communication signals to pass through. This allows for FTL communications in realtime between distant stars.
Each beacon will also transmit its identity into mirrorspace at all times. This signal can be picked up by ships and matched to known beacon locations for the purpose of navigation. The signal has a range of only a few light-years, however, making it possible for unlucky ships that have been swept away by the currents to lose track of all beacons and become lost forever.
Due to their low energy usage, a beacon’s onboard RTG is sufficient to last centuries in deep space or perpetually by using solar converters in a stellar system.

Mirrorgates:

The mechanism required to create a jump point into mirrorspace is bulky, expensive, and requires a great deal of power. Because of this, jump-capable ships are quite rare. Among the allied races, the only ships possessing a jump drive are usually military capital ships, mirrorspace tugs, fleet carriers, specialized freighters, and expensive luxury yachts. Almost all other interstellar traffic consists of ships which cannot form their own jump points.
In order to enter or exit mirrorspace, these ships must make use of mirrorgates, which are enormous framed constructs in space capable of forming a jump point on demand. All mirrorgates include an onboard beacon to aid navigation and interstellar comms. Procedure for activating a mirrorgate is to transmit a request, including either the ship’s ID or valid financial institution details in the case of unregistered ships. The mirrorgate will then activate, creating a jump point that the requesting ship can pass through.
Nearly all mirrorgates are owned and operated by the Navigator’s Guild, who maintains the pricing scheme for gate traffic. Mirrorgates come in pairs, one for ships arriving from mirrorspace and one for ships departing into mirrorspace.
In deep space, these pairs are set up some distance apart to allow ships to burn off etherium, while coasting on their own inertia, before resuming their journey through the departure gate. These gates are fully automated.
At busy ports, where traffic is steady, a different kind of gate is used, consisting of a single structure. Here, the arrival and departure gates are placed back to back, with all the equipment as well as a habitable area for the gate control operator, placed between the gates. These are staffed by Guild personnel and cannot be activated remotely. Instead, the gates activate at set intervals of time or when the operator dictates, allowing batches of traffic through.

Combat:

Combat within mirrorspace is strongly discouraged due to the reaction weaponsfire has upon the various energies native to mirrorspace. Often, even firing a weapon can result in the damage or destruction of the attacking ship. Additionally, performing combat maneuvers within mirrorspace is very likely to result in the combatants being lost in the currents created by the battle.
It is generally understood that if pursuing an enemy into mirrorspace, the target ship has successfully escaped. If the pursuing ship has a skilled enough navigator, the target ship can sometimes be followed to their destination. However, making it known they are being followed is likely to cause the target to pick an exit point advantageous for them.

Linked Portals:

It is possible to create a pair of linked ‘mirror portals’ which make use of mirrorspace but do not require actual travel through the mirrorspace realm. Instead, these portals directly link two realspace locations together as if walking through a door from one location to arrive at another.
Linked portals require a great deal of energy to operate, restricting their practical application to terrestrial use, from one location on a planet to another location on that same planet. Interstellar use would require unfathomable amounts of energy, making linked portals impractical for starship travel.