Great help thank u

Edit: I figured out that my Homstead is under attack and I need to destroy stone in Luculla Forest, I perfectly know where but theres another problem.
I have only 1 weapon with tenebrium attack and its a dagger which I cant use becouse I have 2 man at arms guys and 2 mages.
I read that theres a vendor somewhere who sells tenebrium weapons. Could u guys tell me where?
Edit : found it