Unidentified spaceship

"Colonel, a bogey just appeared on our sensors. Dead ahead, three thousand clicks."

- Erin Gant

The Alien ship was a vessel encountered by the Prometheus in 2004. The race of aliens who built the ship is, to this day unknown.

Overview
The vessel was a starship several times the size of the Prometheus. The ship's technology seemed to be superior to that of the Prometheus, as it was armed with high yield energy weapons capable of depleting a 303's shields in a matter of minutes, and destroying 4 incoming missiles before they could impact on their hull. The craft also possessed transporter technology. It is unknown if the ship possessed shields as they were not seen in the episode. but as the energy weapons were used to destroy incoming missiles and not left to impact the shield it comes to the conclusion that the ship either has no shield capabilities or they used their energy weapons to destroy the missiles as a show of their power.

History
In 2004 when Prometheus encountered the vessel, the ship quickly opened fire, forcing the Prometheus to retreat into a gas cloud. As the ship quickly followed, they both became trapped in the gas cloud but not before beaming the entire crew, save Samantha Carter, off the ship. Eventually though, Carter traded the crew of the alien ship a way to escape the gas cloud in exchange for releasing the Prometheus' crew.