Heian

Heian is a world located within the Milky Way's Arc star cluster. The planet is terrestrial, with a breathable atmosphere and an Earth-like surface. Meteor showers are common on this world, as thousands of asteroids orbit the planet.

Topography and ecology
Heian is a terrestrial world, appearing to be Earth-like and containing a breathable atmosphere for most sapient species without the need of external apparatus. The surface is capable of supporting liquid water and dense jungles of native flora similar to that found on Earth, with much of the observed regions of the planet covered in such a manner. Some regions of Heian feature tiered mesas dotted with immense trees. The planet is subject to regular meteor showers with an asteroid belt encircling the planet—the frequency of which allowing a deployment of drop pods onto the planet to go unnoticed during the Human-Covenant War.

Ruins
The most striking topographical feature on the planet is the presence of ancient ruin complexes predating any form of modern human or Covenant civilization on the planet. The ruins themselves bear resemblance to the stone Forerunner ruins found on Arcadia and Installation 05, mixing a variety of older human architectural trends influences analyzed by Doctor William Iqbal to include Greco-Roman, Middle Eastern and East Asian, with subtle Forerunner themes. East Asian themes are among the most prevalent in the structures examined by UNSC forces deployed in Operation: GREY VEIL in 2544, including decorations containing dragon-like creatures and statuaries distinctively similar to statues of Buddha. Most of the buildings at this site have pagoda-like roof structures. Overall, the designs are very ornate and full of carvings. Curiously, the overall scale of most structures is massive; one step in a staircase may be the height of an average human. Some structures seem like a mix of ancient and relatively modern industrial architecture, including a water processing facility with aqueducts and valve systems nigh-identical to those used by humans. However, some other buildings encountered by UNSC forces during Operation: GREY VEIL feature subtle blue accent lights, a characteristic generally associated with Forerunner architecture.

Another complex later superficially examined by the Office of Naval Intelligence as part of Project BOOKWORM has showcased ruins with more similarities to Forerunner ruins—showcasing the range of architectural styles on the planet's surface. However, ONI teams have only been able to conduct cursory expeditions onto Heian in the post-war environment, with those teams who stayed on-world following the Created uprising uncovering evidence to hint that the ruins may have connections with the human Ancestor civilization that once rivalled the Forerunner Ecumene in the galaxy tens of thousands of years ago. Doctor William Iqbal also considered this idea, noting that the similarities to old-Earth architecture may indicate that the civilization which once occupied Heian almost certainly did not develop those styles independently—and wondering whether they took the architecture from modern humanity, or whether modern humanity took its architecture from the Heian civilization.

Ancient residents
At an unknown period of time several millennia before the advent of human spaceflight in the 20th century, Heian was occupied by an unidentified ancient civilization—resulting in the construction of the aforementioned large temple complexes on the planet's surface. While the identity of this species is unknown, some speculation from modern human researchers has indicated that the planet was inhabited by ancient humanity thousands of years prior to the Forerunner-Flood war.

Discovery
Heian was one of many worlds discovered and occupied by the Covenant empire some time during or prior to the Human-Covenant War, becoming the site of a logistics base used in the empire's genocide of humanity from which supplies were delivered to the rest of the planets in the system, as well as the entire sector. In 2544, the world became the site of Operation: GREY VEIL—a mission assigned by the Office of Naval Intelligence to a small team of Orbital Drop Shock Troopers and a SPARTAN-II supersoldier to investigate the ruins on the planet and assassinate a San'Shyuum prophet. During the mission, the team were also tasked with gathering intelligence on the unknown ruins. The team succeeded in their mission, at the cost of Spartan Cal-141 and ODST Checkman's lives.

Further research
The photographs taken by the team were later studied by the Department of Xenoarchaeological Studies at the University of Edinburgh along with the University of Calcutta as a part of an extensive investigation of Forerunner relics. Following the war's end, further research on Heian was conducted under Project BOOKWORM, with xenoarchaeologist Keely Iyuska leading one of the largest excavations on the planet during or after 2555. The excavation led Iyuska to the believe that many of the structures on Heian may have been constructed by humans in a time period contemporary to the Forerunners. Aside from these excavations, little detailed study of the ruins on the planet was conducted before the Created uprising in late 2558. Despite the crisis, a number of researchers continued to stay on Heian and feed their findings to the Office of Naval Intelligence—presenting the organization with a number of questions about the relationship between modern humans and the ancient human civilization.

Trivia

 * The planet is likely named after either the Heian period of Japanese history, or the city from which the period takes its name.
 * The fact that the ruins on the planet were relatively intact suggested that either the planet was missed when the Forerunners purged the galaxy of any trace of the prehistoric human civilization or that the planet was abandoned during one of humanity's technological dark ages long before their war with the Forerunners.
 * The Halo Infinite multiplayer map Forest is set on Heian.

List of appearances

 * Halo Legends
 * The Babysitter
 * Halo: Evolutions
 * From the Office of Dr. William Arthur Iqbal
 * Halo Infinite
 * Season 04: Infection
 * Halo: Outcasts