I haven't seen any mention of it on here before, but I was looking at my shader collections the other day and came across the Bone Marrow shader. You can get it directly from the blueprint station upon getting all the Kings Fall armor pieces as pre-requisites.
Go and check it out, its on collections page 2 I think. Also wearing it on my Warlock right now :P
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Had it since week 2 of ttk...