As of the time I write this, I would have killed over 50 blades of Crota (and know Eris' entire speech at the start of the fist of Crota mission backwards and in every Xbox 360 supported language) and have had absolutely no luck with the Husk of the pit.
I know you can only get it from blades of Crota, but can't find any stats on getting it, like its drop chance, if there is a certain type of damage you have to kill them with, that sort of thing.
If you have it, firstly I hate you, and secondly, did you have to grind for it or just come across it and what's it like to use?
Thanks,
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I have 2 Well A husk and an eidolon