The Portal Generator, also referred to as the Portal or the Excession at Voi, is a Forerunner artifact designed to generate a massive Slipstream portal that can enable travel from one location to another, usually across worlds and star systems. There are different variants of portal generators and different methods to activating them. Earth's portal leads to Installation 00 and can exclusively be activated by a Forerunner Keyship. The portal generator on Dhaka operates and appears similar to the one on Earth, except it requires specific codes and identification to activate the portal.
The Portal Generators were constructed by the Forerunners as a means to travel throughout space. There are two known variations of this technology. The larger portals can transport ships and fleets across space; the smaller portal transit systems can transport individuals across great distances and even star systems. In addition, there are portals that can cross into other dimensions or even allow one interface with the Domain. Shehaqim is the name of a special portal that links the Domain to the physical world. It is located on Shield World 5040, a valuable asset protected by the Renegade Line designated Line Installation B1-B85.
Before the activation of the Halo Array, the Librarian had a special portal generator constructed on Earth. This device would lead the future mankind to Installation 00 and begin their path to the mantle.
The Prophet of Regret had ventured to Earth on October 3rd, 2552 in search for the artifact that could lead him to the final resting place of the Forerunners, the Ark. He was forced to retreat to Installation 05 upon realizing that the planet he invaded was the heavily fortified human homeworld. Moments after, the Prophet of Truth's arrived at Earth and spent over a month uncovering the artifact buried in Kenya, Africa.
Once the artifact was uncovered, the Prophet of Truth, or rather the ancient Forerunner AI, activated the portal generator and travelled to the Ark. He was later pursued by the UNSC and their allied partners the Sangheili. It was through the portal that the humans were able to end the war, but also through the portal where humanity's greatest hero was lost.
On January 6th, 2553, the portal had collapsed. The Office of Naval Intelligence continued to conduct several expeditions throughout the interior of the artifact in search for a hypothetical control room or other means to reactive the device. Their greatest discovery in this endeavor came when expeditions teams found an auxiliary power station, and theorized that the circuits and power lines could be used to better map the interior and locate the control room.