Ring of Pain

As you are exploring the dungeon each floor will have an exit to the next floor. The standard exits are a simple black doorway, but occasionally you will find an additional exit with a different colour and a question mark above of it. These leads to a new path through the dungeon, such as Reprieve, Assault or Burial Ground. Go through one of these and the achievement will pop.

You can find these new paths as early as the first floor but it is random, so if you don't find one, just keep going down until you do, they are really common.