You need to get the quest "Rumors for an Ancient Relic 1/2". Usually comes up around turns 15-20 range. After the match, the guardian you defeated asks you to "Speak the Place Whence Life Begins" you have 2 choices. You can choose "The Cradle" or "The Grave". Each choice gives you another quest for the next turn. Choosing "Cradle" gives you the "Divine Relic 2/2" quest. Choosing "Grave" gives you the "Cursed Relic 2/2" quest. You need to complete both relic quests for the achievement. This can't be done in one playthrough, so pick one choice and then start another playthrough. When the "Rumors of an Ancient Relic" quest can comes up again, make the other choice.