Tarsis Ultra is an Imperial Dead World that was originally a Civilised World that also possessed certain features of a classic Agri-World since Tarsis Ultra produced food for other Imperial worlds in the Ultima Segmentum. Despite its status as a major exporter of food, the planet suffered from long, harsh winters that gave it the appearance of an Ice World.
The world was the site of a great battle between the Ultramarines Chapter of Space Marines and the Tyranids of Hive Fleet Leviathan in 999.M41. This conflict left a terrible mark upon the world, but Tarsis Ultra was finally transformed into an uninhabitable Dead World by the actions of the Iron Warriors Warsmith Honsou, who unleashed a terrible biological weapon known as the Heraclitus Virus into Tarsis Ultra's Tyranid-altered biosphere.
During the Great Crusade, the Ultramarines, led by their Primarch Roboute Guilliman, were tasked with bringing the world of Tarsis into Imperial Compliance. While on the surface of the planet, Guilliman was attacked by an unknown assailant. During this attack, Guilliman's life was saved by a soldier native to Tarsis, and so the Primarch forged a warrior's bond with the Tarsan soldier, vowing that he and his Legion would return should the people of Tarsis ever need their aid.
A temple was constructed in the Tarsan capital city of Erebus that honoured this promise. The planet's residents also changed the planet's name to include the Ultramarines' name and the local Planetary Defence Force emulated the Ultramarine's Power Armour colours.
In the 41st Millennium
In 999.M41 a splinter fleet of Hive Fleet Leviathan made its ponderous way towards the Tarsis Ultra System and the Ultramarines 4th Company Captain, Uriel Ventris, made good on his Primarch's ancient promise to help protect the people of Tarsis Ultra. On his way to the planet under orders from the Chapter Master of the Ultramarines, Marneus Calgar, he stopped at the planet of Posul to request the help of the Mortifactors Chapter, a Successor Chapter of the Ultramarines and thus also were held by the promise made by their gene-father thousands of Terran years before. The Mortifactors pledged an entire company under the command of the Chaplain Astador to aid in the defence of the world.
Battle of Tarsis Ultra
When the Ultramarines and Mortifactors reached Tarsis Ultra they found it to be a busy hive of activity as the Astra Militarum, along with the Space Marines of the Ordo Xenos' Chamber Militant, the Deathwatch, were preparing the defences for the Tyranid assault.
The forces on hand included two Imperial Guard regiments, the 933rd Death Korps of Krieg led by Colonel Trymon Stagler, and the 10th Logres Regiment led by Colonel Octavius Rabelaq. Also included were the Tarsan Planetary Defence Forces headed by Major Aries Satria.
Upon landing at Tarsis Ultra, Uriel Ventris, Astador, the commanders of the Imperial Guard regiments and the Tarsan Planetary Governor met up with the infamous Inquisitor Lord Kryptman, the man who had single-handedly discovered the Tyranid threat to the Imperium and had led the crusade to stop the Great Devourer.
Before the Hive Fleet arrived in orbit around the planet, the Hive Mind sent out many Lictors to infiltrate the planet's population. These creatures slaughtered hundreds of citizens in the world's rural areas who were trying to fend for themselves and made their way to the largest population centres where they hid in the bowels of the cities, intending to act as sabotage units when the invasion began.
When the Hive Fleet entered the Tarsis Ultra System its first target was the world of Barbarus Prime. The planet was completely consumed by the Hive Fleet and its numbers swelled following this massive intake of bio-matter. The next planet to fall was destroyed not by the Tyranids but by an Exterminatus ordered by Inquisitor Kryptman. This was done to deny the Tyranids access to further reserves of bio-matter that would swell the number of the Leviathan's swarms before they reached Tarsis Ultra.
The captain of the Ultramarine Strike Cruiser Vae Victus, Admiral Tiberius, proposed a plan to slow down the Tyranids by destroying several hydrogen-plasma refinery plants near the incoming bioships of the splinter fleet. This plan successfully destroyed several Hive Ships and slowed the Tyranids' advance.
When it became clear that Tarsis Ultra was the Hive Fleet's next target, the Imperial Navy fleet in orbit of the world, under the command of Admiral DeCorte, engaged the Tyranid fleet in a series of costly battles and was eventually defeated, a loss that resulted in the death of DeCorte and initiated the Hive Fleet's ground assault on Tarsis Ultra.
Defence of Erebus
As the Tyranids surrounded the planet they found that the only thing standing between them and victory was its defenders, who were entrenched around the capital city of Erebus and had heavily fortified it. The city was protected by a high and nearly impenetrable mountain range. The other major population centres around the planet fell quickly to the swarms since they had been relatively undefended as a result of their non-critical value.
Erebus was the most important point in the planet's defence, and if it fell, the rest of the world would quickly follow. The Tyranids filled the sky with a countless number of Mycetic Spores that unleashed millions of Tyranid bioforms after they landed. The first Tyranid troops to make landfall, mostly Termagant and Hormagaunt bioforms, quickly froze to death because of the harsh winter climate, but the Hive Mind adapted the bioforms' skin to better tolerate the cold, and thus the invasion began in earnest.
War in the Streets
While the Astra Militarum and the Space Marines defended the largest and most direct path into Erebus, the city's civilian population was left to fend for itself against the Tyranid bioforms that actually landed inside its confines. During lulls in the Tyranid assault on the main defences, Imperial Guard soldiers would run sweeps of the main streets to kill any Tryanids they found, but many slipped through their net.
While out hunting for the enemy in the streets, a squad of Deathwatch Space Marines and Captain Ventris managed to capture a Lictor alive. This Tyranid was one of the many Lictors that had arrived solar months in advance of the main Tyranid forces, and thus its genome contained unaltered Hive Fleet Leviathan Tyranid DNA.
Inquisitor Kryptman was able to manufacture a toxin from the Lictor's more pure genetic structure that would send an early generation Tyranid into hyper-evolution, killing the creature through metabolic overload. Kryptman planned on using it against the Tyranid Norn-Queen, the strain of Tyranid responsible for birthing all the bioforms of the Hive Fleet. Once the Norn-Queen was dead the Tyranid assault would decay into utter disarray as their link to the Hive Mind was broken.
During the initial Tyranid assault on Erebus, a small gang of under-city youths, led by a ganger by the name of Snowdog, was able to acquire a large cache of food, medical supplies, and weapons from a crashed Tarsan transport ship. The vessel belonged to a Tarsan nobleman and it carried all of his wealth, but during take-off from his mountain complex, the ship had been overtaken and destroyed by flying Tyranid bioforms because his anti-air defences had been offline to allow the transport to reach orbit.
Snowdog and his crew stockpiled all of the loot from the transport in an abandoned warehouse they had been using for cover. Snowdog planned on selling all of the food and medical supplies at a high rate to profit off of the invasion. Unfortunately for Snowdog and his crew, the people who came to the warehouse were poor, and possessed nothing of value, and many started to stay inside the warehouse, using it as a shelter from the murderous monsters roaming the city's alleys and sewers.
Eventually Snowdog had a change of heart, and started to share the supplies with the people, and they in turn praised him for his charity. Near the end of the conflict a Lictor attacked the warehouse and many people, including some of Snowdog's fellow gangers, were slain. Fortunately, the timely arrival of Imperial forces allowed the civilians to be evacuated to the main civilian shelter, the Hospital of Erebus. Snowdog gave the medical and food supplies he had hoarded to the Sisters Hospitaller of the Hospital. Snowdog and the remainder of his gang disappeared into the city with the large amount of weapons that they had acquired.
Assault on the Norn-Queen
The Deathwatch, along with a squad of Mortifactors, the Ultramarine Captain Uriel Ventris and his friend, Sergeant Pasanius Lysane, infiltrated the largest Hive Ship of the splinter fleet to deliver the genetically-engineered toxin to the Norn-Queen. Once aboard the vast bioship, they made their way through the Tyranid-infested halls and corridors until finally reaching the Norn-Queen's chamber at the very heart of the biomechanical vessel.
The Norn-Queen and her guardians fought against the attackers until Ventris managed to finally deliver and kill the monstrous xeno with Kryptman's gene-poison. The Deathwatch and the Mortifactors possessed only sixteen Astartes when the Tyranids started to attack each other in a maddened frenzy, as their link to the Hive Mind had been lost when the Norn-Queen died. The psychic shock-wave of the local Hive Mind's death caused the Tyranids to slaughter each other as if driven insane, leaving the Space Marines alone and able to escape the bioship.
The Tyranids still on the planet froze to death in the harsh conditions of a Tarsis Ultra winter with only a small minority surviving and taking refuge in warmer surroundings. Despite the victory against the Tyranids on Tarsis Ultra, the planet would never be the same ever again. Even though they had been defeated, the Tyranids had left behind their characteristically predatory vegetation, and it slowly consumed the Tarsan ecosystem. The Imperium was forced to leave a large garrison behind whose fire-teams constantly worked, with little success, to eradicate the Tyranid infestation.
Death of a World
Not long after the Imperial victory over the Tyranids on Tarsis Ultra, the planet was attacked by the Iron Warriors Warsmith Honsou. Honsou, who had just won a narrow victory against his rivals, the Warsmiths Berossus and Toramino, had encountered Uriel Ventris on the Iron Warrior's homeworld of Medrengard in the Eye of Terror, where Ventris had managed to destroy Honsou's daemonic Astartes breeders known as the Daemonculaba, which had been engineered to produce new Chaos Space Marines for the Iron Warriors.
Before Ventris could escape, a near-perfect clone of him had been made by one of the Daemonculaba and this clone contained all of Ventris' memories. By using this clone, known as "The Newborn," Honsou was able to learn of the existence of Tarsis Ultra. Determined to destroy everything Ventris held dear, Honsou raided an Imperial agricultural research facility and stole a sample of an experimental pathogen known as the Heraclitus Virus.
Honsou next invaded one of Tarsis Ultra's orbital space stations, slaughtered the crew and launched the station's orbital torpedoes at the planet's surface. While a few of the torpedoes were used to bombard the suffering world's cities, the final one was fitted to carry the Heraclitus Virus.
The virus had been engineered by the Adeptus Mechanicus to speed up crop growth, but when it came into contact with the unnatural Tyranid vegetation scattered across the world's surface, it sped up its growth so quickly that it consumed the entire planet and stripped away the world's atmosphere, leaving the planet an airless, dead rock unsuitable for further human habitation.
After Honsou departed, his vengeance upon Ventris and the Ultramarines complete, the Mechanicus Magos Locard landed with a party of Skitarii to investigate what had happened. Locard vowed to make whoever was responsible for the death of Tarsis Ultra pay.
- Warriors of Ultramar (Novel) by Graham McNeill
- Dead Sky Black Sun (Novel) by Graham McNeill
- The Heraclitus Effect (Short Story) by Graham McNeill
- Defenders of Ultramar (Graphic Novel) by Graham McNeill
- The Chapter's Due (Novel) by Graham McNeill