It's in that valley made by the sword. There's a Root with Nail in most every dungeon, Sewers at either Fl30 or 45 I forgot exactly which, Lich Dungeon at 30, Church Dungeon at 15, and there's a second Root at Crystal/Lizard dungeon at 30
There's one for each dungeon BUT the cardboard one I believe, just keep going down the floors and explore any in the multiplicative of 5 (i.e. 15, 20, etc)
