Wormholes are at least the gate to the ultimate energy sources.

Maybe Kardashev-scale 3 civilization looks like this. 

At the beginning of this text, I must say that wormholes or Einstein-Rose bridges are extreme things. Even if, they would be microscopic. They can transport energy and information from distant stars. And even if we could create a short quantum wormhole. 

That thing would revolutionize computing and information technology. But this text handles hypothetical, large-scale wormholes that could be possible in the distant future. The speed of gravitational waves is the speed of light. So forming the wormhole between the Sun and Alpha Centauri takes 4,5 years. But if those creators can create a black hole that they can use in travel. There is a possibility that they can make that travel. And nobody sees that they ever left. 

That thing makes it possible that they can travel back to the position in spacetime where the black hole formed. So black hole is the time loop that takes the traveler to the beginning point of the journey. And the reason for that is that at a speed that is higher than the speed of light time moves backward. The escaping velocity is the same as the falling speed of the object. So in the black hole, time moves backward because the escaping velocity crosses the speed of light. 

There is the possibility that gravitational wormholes cannot use for space travel. But they can use for transporting the information. In that case, wormholes are like optical cables. That transports information through the universe. 

Theoretically, the wormholes are only two black holes that are superpositioned. That superposition is similar to quantum entanglement. Then the other black hole's energy level must turn higher so that the information starts to flow. In those hypothetical wormholes, the energy flows like in all other systems. 

In some visions, hyper-civilization can make itself timeless. In that hypothetical scenario, the civilization makes a hollow singularity around its solar system. And then the hypothetical civilization makes another black hole in the middle of that solar system. And maybe they could connect multiple solar systems by using those wormholes. 

The hypothetical spacecraft from Carl Sagan's novel "Contact" again. 

If we think of the "back hole spacecraft" from Carl Sagan's novel "Contact" the idea is that the craft is forming two black holes. Its outer core will turn into another hollow singularity. And system creates another black hole in the middle of the craft. The purpose of those black holes is that they should compensate for the gravitational effect of each other. And that means the astronaut will not rip into pieces. In that case, the EEG of the astronaut will make the system oscillate at a certain frequency. 

And if there is another astronaut with the same EEG frequency on another side of the wormhole. That thing makes it possible to synchronize two black holes to the same frequency which is the requirement for the creation of the wormhole. In some hypotheses, the creators of the wormhole network use cloned astronauts. For making the black holes that are oscillating with the same frequency. 

But then we must remember one thing before we are starting to create the black hole networks. The wormhole is the gravitational tornado that closes its internal space away from the outside. But in that system, the energy flows like in all other systems. The energy level of the beginning point of the wormhole should be higher than its end. And that thing is one of the most interesting things in the wormholes. 

If researchers who live in the distant future can create even a microscopic black hole near some blue star like Rigel they can conduct at least energy to Earth. The thing is that the making wormhole that travels to Rigel is harder to make. If some hypothetical researcher wants to make the wormhole that transports information to Rigel. That means they must create the black hole. Whose energy level is higher than the black hole near Rigel. 

But then we must remember a couple of things. The wormhole can be forming between two black holes. The energy level of those black holes must be different before the information starts to flow. So another black hole must be at a higher energy level than another that information can travel in that tube. If those black holes' energy level is the same information doesn't flow.