Little is known about the region of existence known as infraspace. It has been described as a "virtual nothingness" and denoted as the region between life and the Afterspark by Onyx Prime himself, as well as a realm of "pure information". Under certain circumstances, the consciousness of Cybertronians can exist there without a body.
Some ten million years ago, the Thirteen began their interstellar expansion and selected the resource rich world of Antilla as their first colony. The native Antillans fought back, but were unable to match the power of the Omega Sentinels. An Antillan scientist recognized that the conflict would end in his race's extinction and fashioned a doomsday weapon that sterilized all life on the blighted world and transformed the planet into Unicron. The scientist's consciousness would live on in infraspace, spurred on his by hatred of the Cybertronian race. Our Finest Ceremony
During the transfer, Prime's consciousness drifted through infraspace. While there, he felt a sinister presence that seemed to recognize and watch him. Escalation #6 That presence was later revealed to be Nova Prime, Spotlight: Optimus Prime who was, at the time, an undead inhabitant of the Dead Universe and had changed his name to Nemesis Prime. Devastation #3
Following the destruction of Shockwave's chronal drive, Crystal City was swallowed up by the resultant black hole, being compressed into "pure information" and persisting in infraspace, along with Bumblebee though he was left a mind without a body. ...And the Damage Done: Dark Cybertron Finale Endless Forever Bumblebee found himself able to appear as a specter in the physical world, but only Starscream could perceive him, and he wrote Bumblebee off as a persistent hallucination. Bumblebee allowed Starscream to think that and began to serve as the Seeker's "conscience" and a sympathetic ear. The Transgressors
After being stabbed by Storm Shadow, Blackrock's consciousness was transferred into infraspace via the Talisman, whereupon he encountered Onyx Prime. After explaining the Talisman's purpose to his former servant, he attempted to expedite his servant's passing to the afterlife before the spectre of Mike Power came to Blackrock's rescue. Power convinced Blackrock not to flee from his second chance at life. His words reached the Titan Master, who then realized what he had to do and sent out a call to Metrotitan, whom he had transmit an energy wave that acted a cure to the Dire Wraith mutations of the Talisman. The curative pulse had the unexpected side-effect of releasing Mike Power's mind from infraspace, where it found a home in Centurion. Ghost in the Machine
In 2018, Shockwave returned to Cybertron and threw Optimus into the Crystal City singularity, the Prime emerging in infraspace where he reunited with Bumblebee. The Hallowing As the two discussed, Bumblebee noted that everything in infraspace was information and ideas, inspiring Optimus to use the metaphysical weight of the Matrix of Leadership to punch open a hole in the singularity and back into the real world, the two escaping to antespace. Endless Forever Unforgivable
Shortly afterwards, Unicron awoke and was guided by its creator's will to destroy all the Cybertronian colonies. Above Earth, what remained of the Cybertronian race launched a do or die attack on Unicron with Optimus and Arcee following the Talisman to the black hole at the superweapon's core. When the weapon disappeared into the singularity, Optimus leapt in after it, both emerging in infraspace, which presented itself as Antilla. There, Optimus engaged the scientist until both the Talisman rebooted and his allies connected him to the Afterspark. As Optimus began to overpower the creator, the Talisman's energies ravaged infraspace, nearly causing the creator to plummet into oblivion before Optimus pulled him back. As the two made peace, the Talisman finally destroyed infraspace and Unicron itself. Ceremony Having been the one to activate the Talisman, Starscream found himself trapped in infraspace, and fittingly... only Bumblebee could perceive him in the physical world. Post
The term "intraspace" was not used in Escalation, but when Prime later related the experience to Omega Supreme, he referred to his disembodied state as being in "infraspace". Spotlight: Optimus Prime 041b061a72