I like what Omega says about the beacon where the ship lands, but about the ship I like another background story.
What about a ship from another life form which is affected with insects. Those insects kill the pilots and crash/land the ship on a planet. There the life starts with this crashed ship. This can be combined with the beacon/landing platform idea.
Update: But I must admit those reapers look really good and would fit perfectly.
... and about Mass Effects (3) there is no Linux version available. ( No Linux no money ... )