The Ark of Heaven, commonly referred to as just Heaven or the Ark, was a starship built by the Mithraic to transport a small population of colonists from Earth to Kepler-22b. It had a sister ship, the Tarantula, which was hijacked by the Atheists.
The Ark of Heaven was a massive ship with capacity for 1,000 passengers plus an unspecified number of androids. It also carried Landers, which were intended to ferry passengers from the Ark in orbit to the surface of Kepler-22b. In contrast with the ship the Atheist Campion Sturges sent to Kepler-22b, which only needed to carry two androids and some human embryos and could thus move at a speed that would be lethal to living humans, the Ark was relatively slow and required 12 years to complete its journey from Earth. In the meantime, the human passengers were kept in hibernation to reduce supply consumption. While their bodies' metabolism was slowed, the passengers remained conscious and were able to interact with each other through a shared virtual simulation that linked their minds. The simulation was intended to allow the colonists time to spiritually purify themselves of the sins they committed on Earth and prepare them for their new lives.
After the Mithraics prevailed over the Atheists in the Religious War, Earth was left in ruin, with its ecosphere on the verge of total collapse. To ensure the survival of humanity, the Mithraic created the Ark of Heaven to transport a seed population to the "new world", Kepler-22b, where they hoped to build a utopia completely free of war. The Ark took on its 1,000 passengers, mainly the upper echelons of the Mithraic clergy and veteran soldiers, along with some androids, at a repurposed sporting event stadium in Boston in 2145, then set off on its 12-year journey.
At some point during the journey, Heliodromus Otho, a high-ranking clergy member, was able to awaken himself from hibernation prematurely, and used the opportunity rape several women, including Tempest. The Mithraic leadership learned of this horrific crime when they awakened at the journey's end, and planned to have Otho publicly executed.
When the Ark arrived in Kepler-22b's orbit in 2157, Father spotted it in the skies, but refrained from informing Mother. Father decided that with both him and Mother on the verge of failure, it would be best to contact the Mithraic and entrust Campion to their care rather than leave Campion alone. After Mother forcibly deactivated Father, Campion attempted to contact the Ark himself and was able to send a signal via the Atheist ship's communication system. The Ark, which by that point had already deployed multiple scouting parties to the surface of the planet, sent a patrol to investigate the signal. After that patrol encountered Campion and Mother and tried to take Campion with them by force, Mother fully reawakened to her Necromancer capabilities and killed the patrol members with the exception of Marcus, then stole their Lander.
Seeing a way to fulfill her programming after the deaths of five of her children, Mother used the Lander to travel to the Ark, and disguised herself as Marcus to fool the crew. Once aboard, Mother easily slaughtered the soldiers who stood in her way and entered the bridge, then programmed the Ark to crash into Kepler-22b's surface and abducted five Mithraic children.
The Ark of Heaven impacted in a mountain range not far from the Atheist settlement and exploded into pieces. The largest fragments were clustered in the mountains, but a sizeable chunk of the hull was hurled across a desert several days of trekking away. A handful of Mithraic passengers survived in the main cluster of wreckage, including Sue and the high-ranking cleric Ambrose, and attempted to regroup. Days later, Mother scoured the wreckage for omnibiotic medicines to give to the Mithraic children, who were falling ill. The Mithraic survivors took shelter in a cave system to hide from her, then Ambrose, as the most senior Mithraic left, ordered them to set out to find somewhere safer to live. After crossing a desert, the group discovered the secondary wreckage site, where they found Otho and his android guard Leash. By then, Marcus had become leader of the survivors and decided that the secondary wreckage site would be an adequate refuge for the time being.