this is an easy quest however too many people stock on this one.....i have completed all quest 100% so i know some techniques and ill show you how to finish this 1..
easy and gold are quite easy for this 1
look for materials need spells; heal, attack spell and jaggernaut(if you have, much better)...
this is the method i use to complete the platinum easily
the most important units here is the small but terible conscript/cadets
the conscript halt the enemy for a short period of time (the most important method,gives a time for your miner to gather some crystals)
iron golems can't hold the damage of these pathetic mobs thats why you have to bring materials specially the heal and jaggernaut that allows you to increase one's maximim health
now kill this annoying boss