Corridors of Darkness.
To travel vast distances in a matter of seconds, the Nobodies have access to a parallel plane of existence known as the Corridors of Darkness. This power was discovered by the rejection of their gods.
The Corridors are explained as "The space between Worlds." It is a reality where everything has a relative distance to everything else dependent on the size of the traveler. For example, for a single individual, the distance is around 500 feet, so, roughly a ratio of 3:250. For a starship, the distance has the same ratio. In the case of multiple travelers, the Corridor's length is relative to the one whom opened the portal.
The Corridor looks like a long, white plane, with a glass floor. Under the floor is blinding white nothingness. Above, there is helices of grey stretching on to infinity. On either side of the glass floor is jets of blue-white fire, cold to the touch. At at either end is a white, glowing portal, leading from the origin, and to the destination. The portal out does not appear until the user is ready to leave the corridor. The portal from is up to the user's discretion.
A portal to the Corridors of Darkness is vastly different. It always appears as a mass of swirling black smoke and energy. For an extended portal, a black disk of energy and mist, swirling with blue and purple appears on the surface used- typically the ground, but any flat surface can work.
If the surface is a floor, a black arch, with the same mist and energy will grow from the disk, large enough for one to walk through it. If the Door appears on the wall from the get-go, then it will merely grow into this form. In either form, there is a subtle roar from the event horizon, as the fabric of reality is kept ripped open.
If one chooses to make a quick entrance, they can walk through the Door as soon as it opens, and close it as soon as they're through. In this case, it appears that they appear in a puff of black, purple, and blue. Similarly, since the event is so quick, instead of a quiet roar, the noise is more akin to a distorted Timpani hitting a single note.