The Bleed is not a universe in itself, but it is defined as the space between parallel universes. In the Wildstorm Universe, the most advanced beings can travel between parallel universes through the Bleed, or, simply, an arterial duct connecting to universes. Travelling through the Bleed is not without danger though and sometimes objects or beings get lost, appearing in times and places they were never meant to go. In addition, the Bleed has mutagenic properties that alter the make-up of any sentient being that enters it directly. The effects can be beneficial or detrimental, depending on the circumstances of the exposure.
The Bleed was officially discovered by a group of scientists working for Stormwatch. They managed to look through the Bleed at a parallel universe using an opening several atoms thick. This universe featured a Jack Hawksmoor in charge of Stormwatch and he observes the scientists. Later it would be revealed that the Bleed had been discovered before; Jenny Sparks had had contact with the Bleed-travellers from Sliding Albion in the early 20th century and the Planetary had catalogued numerous Bleed incursions. The Bleed would be used for less drastic purposes, such as bringing in new episodes of the television series called The Prisoner.
When The Authority obtained the Carrier, a vessel capable of travelling through the Bleed, Bleed incursions became far more numerous. To oversee the negative effects of these incursions, the Monarchy was created.
It was revealed that there is a hostile force operating within the Bleed that seeks out and exterminates Earths. Its first known attack on the Wildstorm Earth was in 1931 in Rhode Island, involving eggs specifically designed to spawn Lovecraftian monsters when touched by humans; a second incursion occurred in 1999 involving killer robots that could self-replicate. The leaders of this force where shown to be a hideous reptilian version of the Authority.
Bleed-spawned alternate Authorities would show up multiple times in the realm of the Easter Bunny. This realm was inadverently created by the powerful Authority member Jenny Quantum after she reads a violent comic book. Most of these doubles were killed.
After the One Year Later and the Worldstorm events, the Bleed still connects the DC and Wildstorm universes and acts as the space between the restored universes. Captain Atom, after his stint in the Wildstorm Universe, and his brief return in his proper universe of birth, retreated into the Bleed, discovering that the Monitors, still aware of everything about the universe and the Multiverse, are unable to know what happens in the Bleed itself.
As Ion, Kyle Rayner makes his way into the Bleed with the help of the Tangent Green Lantern's lantern. From there he meets Captain Atom who sends him back to his Earth.
The Bleed is the space between Earths of the new Multiverse, with the Source Wall separating the various Earths from the Bleed itself.
Those inside the Bleed: