I have a Husk in the Vault and a Crux of Crota, too. I just never bothered finishing the questline. Is it still possible to complete it? I'd like to, Necrochasm is the only year one exotic I don't have.
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If I remember correctly all you have to do is kill a certain number of thrall with the husk of the pit , then when you do that you can fuse the crux with it.