Well, if we break it down. 'Sadness' is a clear emotion, and 'never - ending story' gives the sense of something that is continuous. As for'seamo o f', it's quite unclear. It might be a misspelling or some very specific term in a particular dialect or sub - culture. Overall, without more context, it's hard to be precise about the whole phrase.
I'm not sure exactly which specific story you mean. There might be various works with similar concepts or names given by different authors or creators.
Well, it's a bit complex. There are several significant names like Atreyu and Falkor. It depends on which character or element you have in mind within the story.