I have a frigid grin main hand weapon as part of one of my builds. When I try to equip it, I get an error message that I cannot equip a duplicate legendary item. I don’t have another frigid grin equipped. I tried equipping a different legendary item and transferring to it but I get the same message. I unequipped all of my legendary items and the game still believes it is a duplicate.
I’m guessing you mean how the essence from the Grim becomes greyed out? This is because you have 2 active Cleave skills on your main hand weapons that can’t stack. It’s not the actual item that’s duplicated rather than the effected skill for the essance
One is likely a transfer item after class changeing. You can’t equip both the created transfer item and the original item the transfer is a duplicate of.