There was a story of two people who made such an impact on the known universe that they were able to change the course of the Reaper War, one was human but the other was of another race that were unheard of in Citadel space, and in the universe. But the stories brought with them untold of horrors that the people of the universe were glad they didn't have to deal with at least on that scale and for a long time for the Reaper war didn't last very long compared to a universe that is always in war, for there is no peace only war. Not only were stories brought with them but the technology they had as well helped change the course of the war, and helped to limit the number of dead which would have been even higher had they not arrived. One of the people that arrived was a ghost of his world for he was one of a handful still alive from a now dead world, and the other became a ghost when she arrived in the new universe having no kin or home anymore, they were ghosts now put together through some twist of fate, the female called it Fate had brought her there while the human had simply said it was the will of the Beati for she foresaw him coming to this universe. But what had the Goddess's planned for them and how did the Beati know of this?
Both of them were said to fought like demons for no one could stand against them and live to tell the tale all people saw were vids of them fighting against, Merc, Soldier, Creature nothing stood in there way, but then once the war had ended they disappeared no one knew where they went or what happened to them, it was like a God or Goddess had sent them there and once their job was done they disappeared. Maybe they are among the people or maybe they really did just disappear no one could say for the truth but everyone knew the human myth of Ghost's and what they were believed to do, people started to believe that they were sent there to avenge species of past cycles and to punish the Reapers but now instead of Reapers after people have claimed to see these Ghost's again they believe that they were still around avenging, helping and punishing the living. Other more weirder rumors say that during the war they were just manifestations of a dead species who were wiped out before by the Reapers and were there to stop the cycle only a few knew the truth behind all of these rumors but they would not speak about it to anyone and maybe this aided them in the reputation they held for everyone feared them. The legend they held was almost as big as Shepard's but the legend was between the right people who knew to be scared of them.
But some knew them simply as people one a human and another a female of another race the Eldar but only a few knew this those who fought beside them and knew them as the people not as the legend. They soon got a name for the duo after the one who had found them and recruited them.
Shepard's Ghost's and this is the story of how they ended up there and who they really were.
(Ok so this hopefully goes the way i want it too, and if there is a spelling or i've used There, Their and so on wrong please point it out otherwise lets try again with this story.)