Also the description of the sword says:
[b][quote]WIth your own hands you forged the mighty Raze-Lighter (...)[/quote][/b]
[b]I bet this is gonna be the exotic you will need to find 50 parts of [u]or this is the "old" and "forgotten" exotic that Eris will give you.[/b][/u]
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#Destiny
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Lauren said that that sword was made during a quest line so yeah, it's a part of some quest but I don't think it's the one we'll collecting 50 pieces for, but idk. I just think they want to save the 50 piece exotic for us to discover.