Anguish IV is the celestial satellite of the planet Anguish, which has long since been abandoned. A short time after the satellite's discovery, it was realized that it (along with the other Anguish satellites) contained copious amounts of Adamantium. Attempts were made to turn this satellite into a Forge World by the Adeptus Mechanicus, but for a reason known only to the Priests on the planet at the time and their Guards, all attempts were halted and all surviving troops were to be pulled out immediately. The satellite and it's three brethren were declared Deathworlds, to be accessed at no times, with no excuses. Any attempts to land a ship on any of the Anguish planets or satellites would result in instant destruction of the ship, and all of it's inhabitants.
A short but extensive survey showed minimal signs of life, and large levels of Adamantium within the inner core of the satellite. It was rare for a world which was not even a planet to contain Adamantium at all, and such levels surely marked a once in a lifetime find. And indeed, this was a once in a lifetime find, but not for the reasons expected.
The plants that were studied on this satellite were incredibly dangerous. The first time an Adeptus Mechanicus priest attempted to study a flower, he was dragged underneath the ground, still screaming. His remains were never found. A group of Adeptus Mechanicus priests were studying a local forest of trees, when one such tree knocked them aside with one of its branches and impaled a charging horned beast with it's other. After this incident, a group of scientists were brought in to study the plants. The experiments that followed showed that these trees were capable of possessing low levels of sentience, and maintained an instinctive desire to protect life. Several attempts to harvest these trees for protective purposes occurred, and after the third attempt the trees became hostile and started attacking every human within whipping or stabbing reach. It is not known how, but all of the trees on the satellite, no matter how far away from the initial attempts of harvesting, will now attempt to kill any human within reach of the trees, hinting that the trees may posses higher levels of sentience then previously thought.