Book of Demons

In order to obtain this achievement you need to finish (not clear+ you can die as much as you want) a game as listed in description. On Massacre difficulty you are given (imposed) a number of cards (depending on the main difficulty you chose for your character), you can not change them during the game (of about 5-8 dungeons). You still can move them in your quickbar and even choose different modifications for the cards, just don't equip any other cards and you shall be fine. Also the Massacre form of this achievement might be the easiest since you have more cards imposed than on lesser difficulties.