Reset your Campaign and Home Realm (your progress for this achievement will not be reset!).

After each mission visit your Home Realm. Mendechaus will say three sentences. At the start (about the last mission). At around 5:20 minutes (something random) and at around 10:20 minutes (about the next mission). Let him finish his sentence before quitting.

Here are all the lines so you know if you’ve heard it.
After each sentence you will get a notification in the debug console (default key is scroll-lock). That looks like: SetStat C*_HomeRealm to 1. Where * is the mission number.

• Mission 1: “If there is a god higher than me… let him rain down chaos upon your head… let’s get cracking Underlord!”
  
• Mission 2: “Come now Underlord, there’s work needs doing. You can continue to make a mess of your realm later.”
  
• Mission 3: “Pah, that Lord O’Theland was hardly a worthy enemy, if you’re looking for a true challenge return to Kairos and challenge Underlord Marcus!”
  
• Mission 4: “Why don’t you take a break from this and go pound some Dwarves into jelly?”
  
• Mission 5: “You’re dungeon is a mess. Clean up your rooms Underlord!”
  
• Mission 6: “Make haste back to Rhasko’ realm Underlord, before the empire finishes him!”
  
• Mission 7: “There are tombs in grave need of desecration, Underlord, return to Kairos and get digging!”
  
• Mission 8: “One of your workers has created a fine rope reed leather pouch.”
  
• Mission 9: “It’s time to claim your prize Underlord, return to Kairos to see what I have in store for you.”
  
• Mission 10: “If you don’t challenge Mira soon I’m afraid you’ll have no change of beating her. Sally forth Underlord!”
  
• Mission 11: “Still biding your time, eh? You should know that your enemies grow stronger as you do…”
  
• Mission 12: “Is it too much to ask that you stay in Kairos until your campaign is complete? You’re almost done Underlord!”
  
• Mission 13: “Now I’m not suggesting you’re mad, but you do have to concede the point that, right now, you shouldn’t even exist!”

After all these messages you’ll get the achievement. In the console you will also get the message: Achievement HR_Listen unlock