On one of the back streets of Gran Soren (the capitol city), there is "The Black Cat" shop. The shopkeeper offers to craft forgeries, in addition to selling his standard stock.
An Arisen must have an item in inventory for him to duplicate. It doesn't matter if the item is carried, or stored at an inn. Choose "About your forgeries..." and then an item from the inventory screen which appears. Give it to him, so that he may copy it.
Be aware that he charges a fee for his forging service, and he demands his fee before he begins. The fee varies according to the item. Some forgeries cost over 100,000 gold, though others cost far less.
For this achievement, it doesn't matter what is forged. However, at specific points in the game it is highly useful to have a forgery of a particular item.
An example: if one is enhancing armor or weapons, and hasn't enough of an ingredient to do the enhancement, it can be more efficient to have him forge more of the necessary ingredient than to go hunting for more. This is especially true of rare ingredients, in which case it is recommended to forge at least one more than is needed, in case one is needed later.
Unless one has obtained the Bitterblack Isle item which makes the forger hurry, roughly two game days must pass before he completes the work (regardless of his claim that it will be ready at that time tomorrow). So either go out adventuring until two nights have passed, or else stay at an inn (any of them, including the 100 gold tent inns or the 50 gold inn at Cassardis) "until morning" ... twice.
Resting benches in Bitterblack Isle won't advance time in the manner that staying at an inn will. Except for not advancing in-game time, they otherwise function exactly as inns found around Gransys do.
Return to the Black Cat shop two game days later, ask about forgeries again, and he will return your original item along with a duplicate.
Some items are indeed duplicated perfectly, and stack with the original(s). Forged magickal items are likely to be unique items, listed as "a forged [name of item]." Those will not function the same as the original, but instead only look pretty.
Examples of items "recognizable" as forgeries include: wakestones, wakestone shards, port crystals, bronze / silver / gold idols, and Salomet's grimoire.
Hope the information is helpful... happy gaming!
