The line comes from The Elder Scrolls IV: Oblivion, released in 2006 by Bethesda. Imperial Guards became famous online for their aggressive combat barks and law enforcement lines, which players clipped for forums, videos and soundboards. Die, Imperial, Die is one of those short taunts guards shout during fights, similar in spirit to other game barks like enemy spotted. It stayed popular because Oblivion guards are a lasting meme, and the shout still signals instant trouble in gaming edits today.