An unknown party was loaned the team to find their missing Acolyte. They deployed to the world and quickly found the large chasm in the earth. They followed it down hundreds of feet, eventually breaching a thick metal plate that went on as far as they could find underneath the ground. The rocks and earth instantly gave way to a hive, one that had not been opened in many many years.
As they searched they found a devolved Tyranid specie that was similar to a hormagaunt. It was bright neon green and attacked them as soon as they detected them. They quickly dispatched them and after the carnage they found the remains of two Imperial Agents and a set of empty manacles. Through psychic will they determined the prisoner slaughtered the two Agents and escaped futyh into the decrepit hive.
They encountered another similar Tyranid offshoot that was breeding more gaunts, these night black with no deviation. They noticed that instead of eyes, they simply had antennas that looked like feelers on a moth.
They encountered a powered section of the hive and found data stacks, but were not able to remove them safely without damaging them. They quickly found the disguised entrance to what lay below the hive.
As they entered the smooth metal hallways and their equipment started to act up, buzzing and communication becoming near impossible. The encountered a large spindly flying monster made of pure silver metal that floated out of the wall. They shot it before it could close the distance, bolters hammering it until it disappeared in a green light. They found rooms filled with skeletal metal frames of inactive soldiers and other rooms that were mysteriously empty.
The energy built as they found a door leading to a perfectly circular room with a figure standing in front of an orange flickering altar. A beam of energy radiated from a pedestal of equipment, trapping a large amber crystal suspended in the air. As they walked in, the figure turned towards them, revealing a figure comprised mostly of metal augmetics. With a flash that dazzled their visors, the crystal broke free and disappeared with a haunting laugh. The figure placed an item on the floor and stepped through it, also disappearing.
After planting the remainder of their grenades in a single spot of the flawless liquid metal room, they escaped, making their way to the surface for extraction.