I'm sure this isn't what you want to hear, but to get the gadwall you'll have to spend two points into the alchemy tree. I highly recommend "recuperation" because the out of combat regen is amazing, then a point into "Witcher secrets" will teach you gadwall and a bunch of others.I haven't found anyone else with this problem, but a formulas are missing from merchants inventory.
For example, neither Fiovaranti nor Master Myron sell the Gadwall potion, and it isn't in the list of Witcher potions you have at the start, so I'm essentially stuck while doing Roche's path, because I can't help Dethmold with his necromantic ritual !
Also, I am still stuck with Raven's Armor I got from my Witcher 1 save, because I can't find any armor schematics. The only one I got was the Kayran schematic, but according to the diagram, it is only +6 ! Never got the schematic from the troll even though I brought back his mate's head, and the list continues.
Most of the things this mod changed are great, but merchants, armors and formulas/diagrams are broken atm.
I'm actually glad that my Raven's armor has lasted this long thanks to the mod. I think Flash changed around how schematics work, same with weapons. They're meant to last a bit longer than they did in the vanilla game.


