You'll have to go to bramble clan and click the blue arrow and go to the left den and put c+m and you type deathberries and kill the guards and you get a vison of the cold stone and you sleep and you'll get the nightmare like robynfur and you can find the black figure in thes places (fire clan) leaders den next to plumclaw and outside the leaders den to the right and the nightmare ends and hell say the words that the black figure tolled you and say ''I'll bring this up to lunarclaw'' you'll get the achievment then.