There is a possibility that there is a civilization that has mastered intergalactic expedition and is all set to be form a Galactic Empire (star wars reference). But, how advance a species or a civilization has to be to master the portals of intergalactic voyage. The Kardashev scale ranks this kind of civilization a Type III.
Type III Civilization
A Civilization that has extracted all resources of its mother Star and utilizes all the energy of their home galaxy is called a Type III Civilization. For a Type III, tugging energy from a Black Hole will not be a very rigorous job. But this is something really big because it obliges the power to control the fabric of space and time. This is about the energy they will heave out of their galaxy , but, how will the voyage be possible? To answer this, scientists thought of the concept of aliens expanding their intergalactic network and connections using something called the Von Neumann Machine.
Von Neumann machines can help to establish intergalactic connections. This device uses self-replicating probes and robots which will land on celestial bodies with low gravity like our Moon where they will assemble a base to develop thousands of extra robots which will travel to even more moons to establish a huge network. These probes and robots can be made with the help of nanotechnology and can be made so small such that they go unnoticed. So, there is a possibility that such a technology exists on our own Moon which we obviously haven’t discovered yet.
In addition to the Von Neumann machine, another way in which such an advanced civilization can travel across galaxies is by a method called ”laser porting”. In this method, the brain is literally “put” into a laser beam which can be sent to numerous stars and galaxies (where a base has been established). When this brain arrives at it’s destination, it can uploaded onto a robot. This is how a civilization will get one step closer to the impossible.