Doisac

Doisac is the homeworld of the Jiralhanae. The planet is classified as a "super-Earth", notably boasting a surface gravity of 2.1G. The planet blurs the line of habitability for most species of the Milky Way, combining extreme surface conditions with

History
Doisac is thought to be a relatively young planet, forming as little as 3.1 billion years ago. As such, the planet is highly active, with plate tectonics and regular volcanism still ongoing. Life is thought to have formed on the planet within the last 500 million years, raising many questions as to how life was able to evolve so quickly on such a young planet. However, the hostility of Doisac's environment ensures that archaeological and geological evidence is near-impossible to ascertain; many proponents of the Out-of-place biota theorem suggest that Doisac may have been subject to tampering by advanced alien civilisations - though evidence of such activites has yet to acquire any real evidence. Due to the young age of Doisac and life as a whole on the planet, Doisac is not believed to have undergone many mass extinctions, possibly making the life currently existing on the planet to be some of the first to arise on it.

The Jiralhanae species are thought to originate around 250,000 years ago, quickly coming to spread across Doisac's main supercontinent. A period of particularly intense glaciation around 175,000 years ago is thought to have dried the seas significantly, opening up many land bridges to the various archipelago islands around Doisac and allowing the Jiralhanae to spread to remote islands, before the following inter-glacial period thawed the polar ice caps and cut off the island chains. This period of cooling and warming is thought to have been caused by the eruption of the Jerion supervolcano located on Doisac's northern hemisphere.

Doisac was later one of many worlds indexed by the Forerunners, and chosen for reseeeding following the firing of the Halo Array around 100,000 years ago. Some archaeological evidence suggests the Jiralhanae had, by this time, advanced to a level of civilisation and technology roughly equivalent with Earth's Iron Age - though this is uncertain. Following the Jiralhanae's reseeding, they proceeded to repopulate the various islands across Doisac to establish a global civilisation. Industrialisation soon followed and by the 10th century CE, the Jiralhanae residing on the Mbreultu supercontinent had discovered steam power. The following centuries saw an explosion of Jiralhanae technology and population across Doisac as new transportation and agricultural technologies allowed the Jiral to populate the planet like never-before seen. This explosion of population and lack of resources soon led to the First Immolation, a worldwide nuclear holocaust which is estimated to have killed between 7-8 billion Jiralhanae. The global wildfires ignited by the war lasted for decades and destroyed almost all life on the surface, leading to a long period of recovery.

Over the following millennium of Jiralhanae expansion across nearby space, several conflicts had Doisac see a few near-misses with asteroid impacts (one natural and several artificially-induced) and a brush with renewed nuclear tensions. By the 2480s, Doisac saw itself the target of a brutal and short conquest by the Covenant empire, following various frontier wars between the Jiralhanae clans and the Covenant's frontier worlds. Covenant warships arrived over Doisac, in 2490, and began a short campaign of orbital bombardment to subdue the planet's polities - predominantly the Co-Dominium of Doisac - into submission. The Co-Dominium soon bent the knee, bringing Doisac into the territories of the Covenant. To ensure the Jiralhanae's compliance, the Covenant established the Station of Sundered Fortune in orbit to act as an official observation post and gateway to Doisac for emissaries and diplomats to meet with Co-Dominium representatives. The station was additionally fitted with a large energy projector for potential glassing against unruly cities. As the Jiralhanae were integrated into Covenant proper, the need to hold a gun to the planet was lessened, and eventually the station's weapons were repurposed for the interests of orbital defense.

During the Human-Covenant War, the valiant service of the Jiralhanae in the campaign against humanity saw a new proclomation given by the Prophet of Truth; in celebration of the Jiralhanae achievements, Covenant engineers were to be deployed to Doisac to begin the lengthy process of re-terraforming the planet back to a habitable state - and even altering the planet's biosphere to be more friendly to life. This deal was made with Tartarus as part of a long series of reforms planned by the Prophet culminating in the Great Schism.

As news of the Schism's outbreak and the fall of High Charity reached Doisac, the planet fell to infighting almost immediately.

Topography
As a super-Earth, Doisac is characterised by its relatively low land area when compared to most garden worlds. Doisac boasts 85% surface coverage as ocean, leaving a total combined land area roughly the size of Africa for the Jiralhanae to live on. This land is spread across the Mbreultu supercontinent and thousands of small islands, including one particular archipelago in the Roghan sea. The planet has a fairly flat and even surface, owing to the intense gravity not allowing for large land formations. As such, Doisac's largest mountains are comparable to the highlands of Earth or Reach.

Mbreultu is mostly comprised of flat plains, grasslands, desert and some jungle broken up by the low-lying Djorian Spine - a series of large hills running north-to-south along the supercontinent and forming a natural divide on the otherwise relatively flat terrain. Four major river networks further break up the territory, with the water erosion accelerated by the gravity to form vast canyons and river valleys.

The Roghan sea lies to the east of Mbrueltu, between the supercontinent and a large archipelago of over a thousand islands. The oceans of Doisac are fairly shallow, with the seabed exhibiting similar flatness to the land. As such, periods of intense sea level reduction are capable of drying certain particularly elevated parts of the sea bed and exposing them to air, creating vast dry salt flats across which land journeys can be attempted. This mechanism allowed primitive Jiralhanae to spread across the sea to the various islands of the archipelago, eventually forming a seafaring culture that would eventually spread to the islands of the northern and southern poles.

As a young planet, Doisac is appropriately extremely tectonically active. As such, much of the planet is covered in volcanoes and gaseous vents - some of these volcanoes form the tallest mountains on the planet, with the pressure of the forces below counteracting the gravitic pull of Doisac. These structures can be found on both land and underwater, and are responsible for providing a near-continuous blanket cover of ash and smoke to Doisac's sky - resulting in near-permanently overcast weather. This layer of smog also serves as an effective blanket for trapping heat and greenhouse gases, allowing Doisac to sustain a large variety of life despite the relative lack of sunlight it recieves compared to other worlds.

Most of Doisac's land lies within the equatorial tropical band - itself extended several degrees both north and south when compared to Earth. As a result, most Doisacian life is adapted predominantly for warmer temperatures. The increased temperature also means that Doisac has little in the way of polar ice caps. Cycles of global warming and cooling do exist on Doisac as on Earth, with the planet's oceans drying considerably to form ice caps in the ice ages. As of the 26th century, Doisac has been recovering from an artificially-induced ice age, and has very little ice to speak of.

Due to the rapid industrialisation of the Jiralhanae followed by the First Immolation and the subsequent lack of dedicated cleanup efforts, Doisac is still coated in radioactive particulate alongside the remains of the potent chemical and biological weapons and industrial waste once deployed centuries ago. This makes traversing Doisac ever-the-more dangerous, as some cities still retain a shroud of poison gas and other toxins, a relic of the Jiralhanae's by-gone industrial era. Cities litter Doisac's surface in a variety of forms. Due to the naturally-occurring seasonal wildfires that ravaged Mbreultu regularly, combined with frequent earthquakes, Jiralhanae engineers in the Age of Legends prioritised survivability and practicality in their architecture over art and aesthetics. The planet's gravity ensures that most structures are squat, with liberal use of pyramoidal forms and supporting columns. As such, many ancient Jiralhanae cities survive into the modern day, despite centuries of neglect and abuse. Some have been reclaimed by the modern inhabitants of Doisac, though many still remain abandoned due to the aforementioned presence of contaminants and radiation.

Atmosphere
The atmospheric pressure of Doisac is similarly high, owing to its gravity. However, this atmosphere is a thin one, with the gravity of Doisac hugging the atmosphere tightly to its surface. As a result, the atmosphere does not extend far off Doisac's surface, and pressure drops extremly quickly at the already-modest altitudes of Doisac's highlands. The higher altitudes experience high wind speeds compared to the relative stillness of the lower altitudes, allowing for particulate in the atmosphere to be quickly disseminated across the planet.

Wildfires and Burns
The presence of fairly dry inland terrain, high oxygen content in the air and ever-present volcanism ensure that Doisac is embroiled in near-constant "Burns"; wildfires ignited through natural processes that are capable of ravaging large swaths of land. These regular wildfires are responsible for replenishing Doisac's soils with new supplies of minerals, allowing new generations of plants to grow. The burns are a regular occurrence, prompting many of the early Jiral tribes to become nomadic in nature, to avoid their settlements being destroyed in the fires. These tribes soon learned to harness the power of mules and chariots, eventually learning to construct entire buildings on wheels, pulled along by domesticated megafauna.

The wildfires of Doisac also prompted the Jiralhanae to begin constructing with more hardy materials such as stone and metal, with Jiralhanae civilisation stabilising between the city-states of the hills, rivers and coasts and the nomadic tribes of the plains.

Ecology
Doisac's native ecology is as hardy as the planet is deadly. Although fairly early on in its evolutionary history, Doisac has evolved a number of potent life forms capable of surviving the planet's brutal climate - almost every life form on the planet can be described as an extremophile in some way.

Fauna
Doisac's animal life exhibits a number of characterists typical of species adapted for higher gravity worlds. Such species' typically squat and often lumbering, using multiple sets of legs at once. In such high gravity, falls can be dangerous, and retaining balance is a key aspect of survival. The typically low-growing flora of Doisac helps ensure concealment for most wildlife travelling on such setups, though larger species' of megafauna do exist, owing to the high oxygen content in the air. Land animals are numerous and have little to fear from the air, due to a scarcity in predatory airborne life. Such creatures do exist, but typically focus on hunting smaller prey or using their aerial advantage to gain a first strike on potential prey, then conducting their business on the ground. Many aerial species such as the Uranaya and its cousins have evolved vast wingspans that allow them to glide Doisac's sky, filter-feeding on aeroplankton and drifting seeds.

The aforementioned aeroplankton operate a curious niche within Doisac's climate. The veritable soup that is Doisac's thick skies are inhabited by vast kilometre-spanning clouds of trillions of plankton-like organisms that drift in the air and feed on the minerals and gases let off by the active vents across the planet. These aeroplankton come in many different forms ranging from almost imperceptible in size to measurng a few centimetres across, and can be found in vast clouds of trillions of members. These plankton float in the higher altitudes of Doisac's atmosphere, and drift across the sky with the wind. Where Earth has blue skies with white clouds, Doisac has almost-eternally-grey skies with large smears of brown - the vast networks of aeroplankton in the atmosphere. At night, tiny flashes of bioluminescense and electrical flashes can be seen emitted by some of these species, flashing and dancing across the sky. The aeroplankton themselves are preyed upon by the aforementioned Uranaya and other similar organisms, alongside Doisac's insect-equivalents.

Due to a relative lack of bright sunlight, Doisac's animal life has evolved to rely on more senses than just sight. In most species, this takes the form of more perceptive olfactory and auditory (smell and hearing) senses. The denser atmosphere allows sounds to travel for longer, and the intense winds can carry potential smells for many kilometres. Inversely, the neat-constant wildfires and bioluminescent displays of aeroplankton ensure that even the darkest nights have a constant level of background light. From orbit, Doisac may be mistaken for having much more land area than it actually does, due to the presence of these aeroplankton creatures,

Flora
Local plant-equivalents native to Doisac occupy a niche some way between Earth's plant and fungoid kingdoms. The flora themselves visually resemble many of the plants found in Earth's jungles, but also exhibit a number of traits inherent to fungus such as mushroom-like "caps", spore reproduction and feeding on decomposing matter. Typical flora rarely grows as tall as Earth's trees, instead settling somewhere around 6-15ft in height, depending on plant. Larger flora does exist, with some tree-analogues able to grow to great heights, and even use

Plants often exhibit vast root networks designed to quickly sap nutrients from the soil around them - often quickly depleting a local area of nutrients if kept unchecked. These plants also have vast, broad leaves designed to provide as much room as possible for photosynthesis. Many plants are adapted to curl inward during rainstorms, to protect themselves from the ash coating their leaves and the bitter weather itself.

To prevent the plants themselves from depleting the area of nutrients to quickly, evolution devised several solutions to Doisac's problems in the form of "parasite plants". This branch of flora serves a similar role to parasites for animals, consisting of plants that grow into and alongside a host to sap them of valuable nutrients. Some of these organisms take the form of ivy-like beings that expand from a single seed to cover large swaths of land, growing on and into local tree-equivalents, ultimately extending their tendrils inside the existing flora to effectively act as an extension of their own bodies, and sap nutrients from these plants in totality. While devastating to a given region, the "ivy" typically overreaches and dies off itself as it kills off all the life around it, ultimately becoming more difficult to transport its own nutrients back to the central "core". These ivys will then stabilise in a given radius or die off entirely.

Another class of parasitic plants are "membranes" - floating discs of organic membrane that float on the wind and eventually land on existing plant life. Upon latching onto a host, the membrane uses secretions to slowly melt into the plant it has attached to, sapping it of useful materials and growing to encompass a large portion of the host, ultimately swelling up and eventually letting loose a flurry of new membranes. These membranes sometimes attach themselves to Doisac's fauna, and rarely an animal can be seen with a membrane entangles or attached to its hide.

Many more of Doisac's plant life thrives on the constant life-death cycle of Doisac. With life constantly dying to wildfires and other means, many species' of plant exist to feed on the dying corpses or the newly-burnt ground, ensuring that even after a major Burn, before long the area will be teeming with life once again. So hardy is the plant life of Doisac that it constantly infringes on the cities, requiring mass-use of defoliants. For many Jiralhanae, clearing away plant growth is a full-time job.

Many plants reproduce via seeds and spores. While many typical methods of reproduction exist, one notable kind of entity leverages the atmospheric ecosystem of Doisac to loose clouds of seeds into the air to be picked up on the winds and drift across hundreds of kilometres. Some of these floating seeds may be eaten by the various filter feeders in the atmosphere, which promptly spread the plants across large swaths of land with their nutrient-rich droppings.