Ignore this. I just read elsewhere you can't do tormented soul + Tenebrium weapon.
Um, I could do it. Found a legendary scythe, which I used a tenebrium bar on, put it to a whetstone and then combined with a tormented soul. Maybe it only works with weapons that aren't tenebrium from the start?
That would make sense. Mine was a weapon I found with tenebrium already on it. Pity, it's a lovely one-hander for my main char!
