To get this you need to start the game and choose Kalig as your 1st soul after playing through the story a bit you will get the quest "Confront Nemek, you son" when your fighting you way through the guild make sure to leave at least one merc alive ...just turn to devourer and go past him/them ...then continue the game as normal.
Now at the end of chapter 5 after killing valkirin return to Thole via the cenotaphs and you will be met with a small cut scene complete the new quest (Be prepared lvl 28 boss fight to come!!) upon completion the achievement should pop ….DING on to the next one