The vessel was a spaceship 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 (33 shots), 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 because the ship's energy weapons were used to destroy incoming missiles. This could mean that the ship either has no shield capabilities, or they used their energy weapons to destroy the missiles as a show of their power.
In 2004 when Prometheus encountered the vessel, the ship quickly opened fire, forcing the Prometheus to retreat into a gas cloud. As the ship rapidly followed, they both became trapped in the gas cloud, but not before beaming the entire crew, save Samantha Carter, off the ship, presumably as a means of leverage to force Carter to work on a way of getting both ships out of the cloud. Carter later traded the crew of the alien ship a way to escape the gas cloud in exchange for releasing the Prometheus's crew which the ship accepted. It later held up its own end of the bargain by transporting the Prometheus crew back to the ship. (SG1: "Grace")