Kenyan Excession

The Kenyan Excession, variously known as the East African Excession, the Mombasa Excession, or simply the Excession; as well as the Kenyan Artifact, Ark Portal or Portal at Voi or the Hallowed Gateway by some religious groups, is a prominent Forerunner artifact located between the cities of Mombasa and Voi in Kenya, East African Protectorate, on Earth. The only known surviving slipspace portal generator linking to the extragalactic Installation 00, it continues to be one of the most strategically relevant Forerunner sites known.

The Excession's uncovered portion is a convex disc approximately 117 kilometers in diameter, lined with projection spokes that unfold from the dome upon the portal's activation. While its full extent is unknown, it is evident that the artifact is considerably larger than its visible part, possibly reaching kilometers underground particularly around the center of the dome.

Construction
Buried in the earth around 100,000 years ago by the Forerunner known as the Librarian, the artifact was built as the last of a network of slipspace portals used by the Lifeworkers to transport indexed specimens to the safety of the Ark as part of the Conservation Measure.

Rediscovery
For much of history, the portal lay beneath on average a kilometer of granite and basalt rock, perfectly landscaped by the Forerunner machines to match the native terrain. The earliest indications of the artifact's existence came in geological surveys conducted in Mombasa in the late 23rd century in preparation for the construction of the Mombasa Tether and the accompanying expansion of the city. The Office of Naval Intelligence quickly took interest and took over the excavations shortly afterward. A subterranean facility now known to be a small section of the portal's outlying infrastructure was partially uncovered, but progress was slow. ONI sought to turn the entire Mombasa area into a black site in order to safely continue the excavations on a larger scale, but had to concede to political pressure from the East African Protectorate and the United Earth Government. A compromise was reached, with ONI being allotted a prominent regional base in the southeastern end of Mombasa Island as part of the sweeping reconstruction program accompanying the space elevator's construction. In addition, ONI retained control of the lower levels of the city's subterranean infrastructure and were allowed to continue their research into the ancient artifact. Progress was modest, due to both restrictions imposed by the megacity lying atop the excavations, as well as the impregnable nature of the artifact. While some archaeologists suspected the relic was larger than the portion already uncovered, none predicted its true scale, with most estimations confining its extent to the area north-west of Mombasa Island.

The Excession was fully uncovered for the first time since its burial in the fall of 2552. Seeking to access the Ark, the Prophet of Truth's Covenant fleet excavated the relic during the weeks between October 21 and November 17. On November 17, Truth landed in the center of the artifact and used the Covenant's keyship, the Anodyne Spirit, to activate the gateway. Truth and the Covenant fleet subsequently entered the portal, followed shortly after by the Schismatics' Fleet of Retribution and elements of the UNSC Home Fleet. The activation of the incomplete Installation 08 over the Ark destabilized the portal, severing the connection. This cut the transiting Forward Unto Dawn in half, returning its fore half to Earth while the aft section, with Spartan John-117 aboard, was sent into unknown space.

East African Exclusion Zone
Following the battle, the excavation basin was filled with seawater, reaching the low-lying edges of the Excession's disk. The site was promptly quarantined by the UNSC, becoming known as the East African Exclusion Zone. The Zone was relatively easy to close off, as the region had largely emptied of civilians during the months of the Covenant invasion. Few also sought to return, as large swathes of the Zone remained devastated and barren due to the Covenant assault along with the Schismatics' subsequent glassing of Voi and its surroundings to contain the Flood outbreak there. Still, this posed challenges as to the relocation of the displaced population, as the Zone covered several previously-bustling cities, including Mombasa, Voi, and Arusha, the historical administrative capital of the EAP.

In the Treaty of Arusha, the Excession, along with the Ark beyond it, was defined as one of the "Forerunner sites of strategic importance" to remain under joint control between the UNSC and the Concord of Reconciliation, similar to the Halo rings. In practice, the Excession remained under UNSC control with an observer and specialist presence by the Concord. Before the artifact could be properly studied, the basin and several of the surrounding underground caverns had to be drained of saltwater, requiring the construction of large seawalls in the inlet region where New Mombasa once lay. Even after this was accomplished, in the second half of the 2550s, research proceeded slowly. The eventual goal was to find a way to reopen the portal to the Ark, though it became clear that without an intact Keyship, this would likely be impossible. ONI remained in charge of the archaeological efforts, though most of the researchers themselves were civilian contractors, led by Doctor William Arthur Iqbal. However, all civilians at the site were carefully vetted by ONI, and outsiders such as representatives of the media were rarely allowed in. The UNSC's main base of operations in the Exclusion Zone was the Mombasa Annex, an ONI installation built in the remains of the base of the collapsed Mombasa Tether.

The boundary of the artifact site quickly became a prominent religious site and pilgrimage destination, mostly for ex-Covenant but also a number of human neo-religions. The latter include the Celestial Highway, largely seen as an imitation of the Covenant religion, the Atlanteans, who liberally combine classical mythology, various world religions and elements of Covenant beliefs, and the Manuelite sect of Nuvangelical Christianity, which conflates Biblical accounts with the Forerunners. However, the UNSC maintained a strict no-access policy within the Exclusion Zone, not allowing civilians, human or alien, within a hundred kilometers of the artifact without thorough background checks, registration and military escort. A special filter was maintained on non-human visitors, who had to be specifically authorized by the Concord consulate within the Silver City. A no-fly zone would also be enforced around the Artifact, with trespassing craft forced to land or be shot down. It was not uncommon for alien cultists to attempt entry despite this, though as this became commonly known, most pilgrims were content with congregating in nearby cities, most prominently the megalopolis of Dar es-Salaam.

The Excession remained a pressing point of astropolitical tensions between the UNSC and post-Covenant factions. While it remained inert for the time being, the fact remained that if the portal could somehow be reactivated, those who controlled it would have access to the vast treasure trove of industrial capability and knowledge that was the Ark. Some Sangheili continued to maintain that the artifact should not be allowed to remain in human hands, as they would likely exploit the resources of the Ark to dominate or even exterminate other species as retribution for the genocide they were subjected to. Such cynics were hardly assuaged by the Concord's presence at the site or the Treaty's specification of joint-species jurisdiction for the Ark, maintaining that humanity would likely seize the relic for themselves anyway should the gateway be reopened. the Arbiter continued to maintain that the Concord could easily enforce joint control of the relic if it came to that, and continued to highlight the role of the Sangheili's own actions in proving they were trustworthy allies, thus eventually changing humans' views to the point they would no longer regard retribution as desirable. Even so, the underlying tension remained even as the Arbiter and his inner circle managed to convince most commanders to focus on more pressing issues at hand. Well aware of this, the UNSC continued the decentralization efforts initiated under the OUROBOROS Directive to increase humanity's resilience and extrasolar presence in the event of another invasion, while also fortifying Sol as best they could along with an improved early-warning network set up across human space. By the late 2570s, this underlying tension erupted into conflict, as various Sangheili warlords exploited the growing unrest within the Concord and mobilized to seize the portal site.