Heroic: Worlds Ahead

Be aware that you only need 15 out of ALL the World Quests in Val or Naigtal to get this achievement

World quests in Naigtal is:

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• Mush-Vroom!
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• Mashing Mushroom Mana Machines
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• Scrubbing Troubles
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• Power Overload
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• Sporadic Power Drain
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• Marsh Mana Spores
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• Skiff Joyride
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• Forest Mana Spores
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• Crypt Culling
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• Weaken Their Forces
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• Flying Debris
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World Quests in Val are:

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• Lingering Corruption
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• Freeze Range Eggs
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• A Lingering Echo
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• Ignoble Gas Collector
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• Junction Dysfunction
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• Solid Cold
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• Shadowy Strategies
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• Dissent and Divide
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• Cold Reception
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• Tainted Ritual
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• Until it is Done
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• Aberration Liberation
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• Caver Saviour
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• One Friend is Plenty
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• Aberration Liberation
• 
  

Thank you BananaBomb :)

I have no idea why, but most of the world quests doesn't count for this achievements. Looks like bug

Naigtal
Mush-Vroom!
Scrubbing Troubles
Sporadic Power Drain
Skiff Joyride
Crypt Culling
Flying Debris
Mashing Mushroom Mana Machines
Power Overload
Marsh Mana Spores
Forest Mana Spores
Weaken Their Forces

Val
Lingering Corruption
A Lingering Echo
Junction Dysfunction
Shadowy Strategies
Cold Reception
Until it is Done
Caver Saviour
Freeze Range Eggs
Ignoble Gas Collector
Solid Cold
Dissent and Divide
Tainted Ritual
Aberration Liberation
One Friend is Plenty