STEPS ON THE PROCESS--------------------------------------------------------------------------

Step 1-find the sphinx at the mountain shrine (accessible via Worldsend cave, and or Misty marshes).

Step 2-Talk to the sphinx and select the "Riddle of Conviction" (get a quest for finding and giving the sphinx something valuable).

Step 3-Figure out what item you want to give for this play through (any of the named item types above will suffice).

Step 4-Talk to the sphinx and go through the riddle of conviction prompt to get the window that will ask you to give the item.

Step 5-after going through the sphinx's prompt and her warning about "not getting the item back" which is a lie, you'll then be directed to the chest she just recently unlocked which will have the item you gave.

Step 6-Once you looted the chest and now have the item notice that when you check your inventory you will have your returned item, AND MORE IMPORTANTLY CHECK YOUR MAIN PAWN'S INVENTORY THE ITEM WILL ALSO BE THERE.

Step 7-Get motivated to duplicate what ever you want in the future but only once per play through so get new game + ing.

I hope this guide helped because i tried doing research and it was not much of a topic that is brought up and not much documentation on the duplication process. This method is probably the most legitimate and vanilla way to duplicate a item on a 1:1 ratio and i don't think this will get patched any time soon as if it was intended. One last thing this strategy and method can only be done once per play through as stated multiple times above so in a way it seems strongly balanced already.