Originally posted by Soulstinger:

I ended up having to look up the item they are referring to and I would suggest to the devs that it isnt intuitive, especially for those who didnt interfere with the Dverger

One of Odin's ravens, Hugin, tells you the first time you go near a root (which you'd realistically have to have done by the time you found and cleared 2 Infested Mines) the following:
"Kraa! Although severed from the trunk, I can see that magic still lingers in the roots of the old ash. Needless to say, no weapon of your own design will be able to break the bark. You need something better, fashioned by more capable hands."

This meeting with the raven is literally my first screenshot ( I take screenshots of anything new or interesting in game to chronicle my adventures and so I can look back on it later) in the Mistlands. The one before that was me starting my chicken farm, before that the first wisp coming to the fountain. If this riddle is too complex, then I'd suggest a less difficult game, like tic tac toe.

There are a lot of difficult/challenging things in the Mistlands. This is not one of them. The confusing part here for many is mostly the significant barrier to entry for crafting Mistlands gear that is not so present in previous biomes. I had a couple hundred sap collected by the time I found and cleared my first Infested Mine.

I will say that I think there should be an alternative way to get the necessary item. Dwarves clearly like to barter...