Found in the Giantwoods, at the start head towards the southeast, then move northeast when you get to the questgiver with the 3rd moonstone. You will have to cross a large stone bridge guarded by an ogre like creature.
Just after the crossing, head north and there will be another large battle near a portal. When the battle is done, two stone faces will start to talk about how all the old hunters were so good. Then they will drop the botched armor. Pick it up and the achievement will pop.