Dragons Dogma Dark Arisen

When you go to the Black Cat to make a forgery you have to choose an item that'll create an imperfect forgery. Magical items like wakestone shards are easy. You can just buy the shard at the Black Cat and then have him forge it. Sleep for the day and grab the imperfect forgery. Pop goes the achievement

If you want to save money. Climb a nearby ladder and head to the roof of the Black Cat and go inside the open doorway. The chest there has a Wakestone Shard forgery.