They laid mostly dormant since the Scourge, an apocalyptic event that released energy that destroyed the Jardaan and was the reason why the Andromeda Initiative’s intended colony worlds were damaged beyond habitation.
The Remnants were caretakers of the Jardaan’s massive terraforming technology. Ryder discovers a new synthetic race called the Remnants built by the long-deceased Jardaan. RELATED: Mass Effect: How C-Sec Became the Galaxy's Premier Peacekeeping Corps Ryder becomes involved with helping the Angara resistance against the Kett while searching for the missing Arks and habitable worlds to colonize. The Nexus is in disarray, undersupplied and understaffed due to the missing Arks and almost on the brink of collapse. Ryder’s Ark can only make contact with one of the other Arks, the flagship Nexus, which was designed to be the base of operations for the Andromeda Initiative and intentionally modeled off of the Citadel. In addition, when Ryder arrived in the Heleus Cluster of Andromeda, they found themselves embroiled in a war between two native alien races, the wary Angara and the vicious Kett. Arriving in the year 2819, roughly 630 years after the original trilogy, Ryder discovers that none of the worlds the Andromeda Initiative planned on settling turned out to be what they needed.
Players assume the role of Ryder, a colonist who takes on the role of Pathfinder following their father's death and is saddled with the responsibility of finding habitable worlds to settle on. The Arks’ occupants were held in suspended animation, only to be awoken upon arrival. The Andromeda Initiative intended to launch six massive ships called Arks on a one-way trip to the neighboring galaxy, though only four are known to have launched (the arrival of the fifth Ark was planned for DLC that was never produced). Andromeda's story really begins between Mass Effect 2 and 3 and revolves around the Citadel races' joint-colonization effort.