Bolder's ring, more commonly known simply as the ring (or the Xeelee Ring), is a highly advanced Xeelee structure and one of their greatest achievements.
The ring has a diameter of 10 million light-years (100 times that of the Milky Way galaxy) and is made of cosmic superstring. The Xeelee constructed it over the course of billions of years during which they converted the mass of thousands of galaxies into the ring's superstring. The ring spins near the speed of light, which combined with its mass, causes the creation of a naked singularity at its center. The enormous mass of the ring locally counteracts the expansion of the universe.
Twenty-first century humanity was aware of the gravitational anomaly created by the ring and dubbed it the Great Attractor. Upon discovery of the ring itself, humanity mistakenly assumed it to be a weapon, while instead it is a portal used to escape the universe.