I just put 2 and 2 together and from what people have said the sleeper simulant quest is 50 pieces and there's 50 calcified fragments on the dreknought once I've found all fragments I'll share what the out come is but this is my only theory for now also just saying remember bungie them selves said it is a 50 part quest and all 50 are found on the dreadnought and the legendary pocket infinites are found on all planets calcified fragments are not found on all planets there only found on the dreknought and there's 50 of them look it up you're self if you don't believe
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The calcified fragments are for something else. The Sleeper is the exotic railgun. You get the quest by gathering up the Rasputin Relics. They look like legendary Pocket Infinity fusion rifles with a weird ass name.