I'm not sure if this being looked into yet. But I figured I'd make sure someone reported it.

There seems to be a bug; that allows you to use the same set of reagents, to imbue the alchemy bonuses on multiple thrown weapons. Confirmed at Alchemy level 22 (with both +2 rings) & 23 (without the rings).

Make sure to start with enough alchemy reagents, to imbue at least 2 of what you want to imbue.

1) Open Alchemy
2) Select whatever weapon bonus you want (+ fire for example)
3) Right click a thrown weapon stack (though not thrown potions), and add the item to the mixing screen
4) Click 'Mix'
5) Move the imbued weapon into your inventory
6) Select the same alchemy option you selected in step 2
7) Right click the same thrown weapon stack, and add the item to the recipe
8) Do *NOT* click Mix
9) Instead; pick the item back up (click) from the mixing screen, and place the not-yet imbued thrown weapon on the stack of already imbued thrown weapons
10) Kapow! You now have 2 imbued thrown weapons, for the reagent cost of one
11) Rinse/repeat for as many of those particular specific thrown weapons you had in the original stack
12) When done, put the unused reagents back into your inventory
13) Sell the imbued weapons to weapon vendors for absurd amounts of gold (example: make a bunch of +3 Fire Damage stones, valued at 501 gold each).
14) When the vendors run out of gold; simply go sleep it off for a week (in game) while they refresh their gold supply (foraging helps pass the time, and gives you reagents to sell to the other vendors).

Note: Additional types/specs of thrown weapons require a new set of reagents.

Edit: Must learn to proof read before submitting...

After further review; you can actually skip steps 6, 7, & 8.

You can just go straight from stack A (regular) to stack B (imbued), and the imbuing happens automatically.

Confirmed - good find!

It looks like the game lets you merge stacks of items with different properties but the same name, resulting in a single stack of all one kind or the other. It works both ways - whichever kind you're adding to is the one that stays. To replicate you'll need a stack of at least two thrown weapons, alchemy of at least 5, and the ingredients for a weapon imbue - ectoplasm/sulfur, ectoplasm/ash, and black-spotted shroom/noximander venom all work at alchemy level 5.

• Imbue a single weapon from the stack
• Put the imbued weapon in a spot in your inventory
• Pick up the rest of the stack of non-imbued items
• Drop them on the imbued weapon

I guess this isn't a big surprise given that the game typically only checks item name in many situations. The obvious fix would be to verify that all the properties of two stacks of items match before combining them, but I don't know how much of a pain that would be to code. A more subtle fix might simply be to change the name of imbued thrown weapons, the same way as is done for melee weapons and bows. Unless the names are distinctive between +1/+2/+3 of each kind of imbuing and all combinations, though, it would still be possible to exploit.

Honestly, though, the thrown weapon specialist deserves a break like this. Aside from the gold farming aspect of the bug, I'm not sure it's worth fixing. It might be nice in Book III simply to allow imbuing whole stacks of thrown weapons with a single set of reagents, unless of course BW has other plans to improve thrown combat.

I think this has something to do with the subroutine for identifying and stacking items. The real "bug" part of it is when you have some items identified, put them in a storage container, come back with unidentified items of the same type and quick-loot from the container, you forget what the stored items were rather than them identifying the new items.