Avengers Mountain

According to Loki, the Progenitor was an Alpha Celestial who came to Earth four billion years ago after being infected by the Horde to die a sad and painful death. The Celestial's diseased body fluids seeped into the Earth and percolated through the planet's primeval surface, forever altering the Earth's evolutionary trajectory. Loki further claimed that this process constituted the primordial cause that gave rise to the mutations and superhuman abnormalities present in many of Earth's inhabitants. The Progenitor's corpse laid unmoved within the Arctic Circle, and its resting place became the bottom of the Arctic Ocean at the North Pole.

After Loki facilitated the arrival of the Final Host of Dark Celestials with the objective to purge the Earth, he captured Captain America and took him to the Progenitor's resting place and told him its story.

After the Final Host was defeated by the reformed Avengers, the resurrected First Celestial Host brought forth the Progenitor from its watery grave and bestowed it upon the Avengers as a gift to serve as their new headquarters and a reminder of the wonders of life on Earth.

The Avengers Mountain comes equipped with living headquarters for each member of the team, a gym, a laboratory, and docks for ships. Every floor of the building is connected through a sophisticated elevator called the Spinal Lift. The Avengers managed to partially reanimate the Progenitor's circulatory system and use the cosmic energy from its blood cells to turn one of the ventricles of its heart into a teleportation hub with global reach called the Circulator. The remains of the Celestial's cerebrum were retrofitted into a server room, housing the most powerful computer terminal in the galaxy with the potential to decrypt countless data stored within the brain tissue. Each finger of the Progenitor's right hand was turned in a hangar and the intestinal tract into a detention facility.