Forerunner (Earth-9791)

The "forerunners" (Latin: Primoris prognatus, meaning "first born"), are a seemingly extinct sapient species who built a thriving civilization on the planet Tau Volantis millions of years in the past, until their discovery of a Marker.

Early history
Approximarely two million years in the past, the species only known as the forerunners developed a thriving civilization on the water-rich planet of Tau Volantis, with both an advanced technology and society. However, after years, they discovered an ancient artifact buried in an ocean at their planet. They soon began to worship the relic, which promised a new, effectively limitless source of energy for a brighter future. The extraterrestrials constructed artificial Markers across the surface of the planet, hoping to gain more energy. However, they soon discovered the Marker was sapient, revealing its true intentions.

First Convergence Event
A violent outbreak soon broke across Tau Volantis, killing, harvesting and hosting its population into monstrous creatures, enslaved into the will of the Marker. Once enough of the forerunners had been killed to provide enough biomass, the Markers began the Convergence Event, assimilating the collective intelligence of all hosts to form a Keymind that could continue spreading across the galaxy.

The surviving forerunners were able to construct a massive machine capable of flash-freezing the planet, halting the Convergence Event and preventing the Keymind from proceeding with its infection. However, this led to the extinction of the forerunners themselves.

Legacy
At least one forerunner was able to escape extinction, fleeing Tau Volantis, most likely under the Marker's influence, with numerous Ovomorphs aboard a ship. The alien crash-landed on the moon LV-426, in the Zeta Reticuli system, where it remained for the next millions of years, fossilized.

The fossilized remains of the forerunner were found on June 16th, 2525, by the crew of the human freighters Nostromo, which landed on Acheron on June 16th, 2525 after acquiring the signal from the derelict at LV-446. Despite the fact the ship's Shaw-Fujikawa translight engine was damaging during the landing, Captain Arthur Dallas, First Officer Thomas Kane, and navigator Joan Lambert formed a trio to explore Acheron's surface, eventually discovering the derelict and the signal coming from it. While they explored the ship, the trio discovered the fossilized remains of the ship's pilot and the many Ovomorphs that were stored on the ship for reasons unknown. Once Kane approached them, he was attacked and impregnated by a Facehugger. Dallas and Lambert then took Kane back to the Nostromo, which departed from the moon. Hours later, the xenomorph that had been incubated on Kane birthed aboard the ship, leading to the massacre of the crew and the destruction of the vessel.