Dungeons 2

I did this achievement on the last single player map. Just destroy everything around Krowtoes and then retreat.
Nothing more will spawn.

Use your Goblins to upgrade everything collectable related and then get rid of them and your trolls. Get lots of little snots and nagas.

Demolish all the wall and collect away.

The level has 5 mana crystal and lots of gem/gold mining. You can easily finish both the power be with you and Dark gold rush achievement here.

Be sure to save a few times in the level. if you run out of resources, you can always reload a previous save.