There are two ways to duplicate items:
1. There's a device in the Catwalk Caverns (near the end of the game) that let's you duplicate one item. In order to activate it, you have to push three Necrosaps (those flying sparks) between the shocking things (you'll recognise them when you see them).
2. There's another way to duplicate items, but it works by (ab)using a glitch. I'm quoting myself from
http://www.ethereallore.com/1cheats.html.
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Cheat! I've found quite an interesting bug - it lets your might and protection grow to infinite!
Note: I have CD version 1.02. I think this worked on and older floppy versions as well.
Here's the trick:
1. Go to White Tower Lv.3 (or Castle Cimmeria Lv.1 but that is too far away and too late in the game to really make use of this cheat) and go to the only pit in the level (the pit which drops you off at the minotaur on Level 2). Save your game.
2. Make sure the pit is open. Wait for a ghost to appear over the pit.
3. Now, place a weapon or armor (preferably Great Sword 'Justice' or the Kite Shield) on the pit, so that the weapon or armor falls through. The ghost will have disappeared.
4. Click on the pit and you'll get your weapon/armor back (keep trying, it might be hard to find the right spot). Place it into your inventory. Keep clicking on the pit and you will get more copies! Get a number of five of the same weapon, or four of the same armor.
5. Go to Victor's Arms or the weapon seller in the swamp.
6. Equip your party with all copies and sell the remaining one.
7. Go outside and check your characters. Where the equipment was are now items named 'illegal item'. Take them all off and place them in your inventory (NEVER place two or more copied items or illegal items on the floor--the game will crash). While doing this, your might/protection will not decrease and will remain the same as when you were equipped.
8. Get back in the shop and re-buy the same weapon/armor. Your 'illegal items' will re-change to the copied equipment.
9. Repeat steps #5-#7 for infinite might/protection.
Notes about the steps above:
-I decided to actually check what I mailed you earlier and to my shock I discovered that an important piece of the infinite might/protection trick did not work; when you re-buy a copied item, the "illegal items" do not change back to the copied item. I guess that part only worked on older floppy versions.
-You can still get the trick going in the CD version; equip yourself with all copied items and sell the remaining one as usual. Buy the equipment back (or choose another item to copy). Now, go back to copy your equipment and repeat. To get rid of "illegal items," donate them to the "Stone Idol: Ra’ToI the Fortunate" in the swamps (refer to the map). It just costs a lot more time, but you also get infinite money this way.
- Watch out for enemies that grab your weapons and drop them on the floor--remember, if two or more copied items or illegal items are on the floor, the game crashes.
- This trick is best done with Great Sword 'Justice' or the Kite Shield, because you can re-buy them in the shops.
- If a character now wears no weapons or shields, it can damage enemies with his bare hands!
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As for the Emerald Blade, I don't know which one you've missed, but there's one in a treasure chest in Upper Opinwood and the other one is in the Urbish Mines level 1 (part 2), somewhere on the floor. Good luck!