Wormhole stations

Gargantuan megastructures of Precursor origin found throughout known space. They most likely linked their entire empire like a spider web; now mostly closed. While the Precursors disappeared, the Deshivohai still keep them in functioning condition, although rarely granting passage to any passing craft.
Humans managed to have been granted access to two of these stations, namely the Proxima Centauri Station and the Nijin-Laj station.
Like most known Precursor technology, these structures are metamorphic, being able to change shape drastically as if they were organic.
Deactivated stations assume the shape of a perfect, smooth, sphere light azure in color with no seams or other such sign of it being a wrapped up technology. Once activated the station unwraps into two main arms and a central, circular section, containing a raw, highly concentrated nucleus of inactive Exomatter which the station probably uses to fuel itself and morph; from this section four tentacle like protrusions move to surround the travelling craft; the central section will then start rotating faster and faster and then you find yourself suddenly at your desired destination (being the closest station to it), looking at another active station like the one before, just this one is not operating on you.

Manufacturing

Manufactured by the Precursors durig the heigth of their empire, probably as waystones during their travels around the cosmos.
Such enormous structures must've required improbable amount of resources but no construction site has ever been discovered in the limited time Humanity traveled open space in uncharted routes.
The dilemma remains unsolved as both the stations that have been observed don't seem to originate from the system they're located in as the latter is untouched.

Access & Availability

Precursor technology only available and usable by the Deshivohai, although they'll grant passage to other lifeforms in determinate conditions.

Complexity

The inner workings of the stations are out of reach for Human comprehension, even the wormholes they create are different from what physicists hypothesized they would be.
Precursor wormholes are invisible fields that you don't need to traverse, once ready the craft will immediately be transported to its destination, coexisting for an instant in both places at once but at the same time without ever moving, like if you never were in the starting position at all.

Discovery

First discovered by the Humans returning to Earth while passing near Proxima Centauri.
While doing a slingshot manoeuvre around the star, they reported an enormous megastructure in the celestial body's orbit, fearing it may be Reshtu technology, they fled the scene.
Only decades later, with the first colony ship, they were hailed by a then thought to be pre-recorded message inviting them to use the station to reach their destination. Now we know they were hailed by the Deshivohai manning the station, aware that Humanity was looking for a new home. Interestingly the Deshivohai already knew human languages to an extent they were able to communicate with us.