How to complete the Goblin King quests in The Forge

The Forge certainly isn't lacking when it comes to RPG-inspired sidequests, as the mining sim is chock full of lengthy NPC chores and requests with valuable rewards distracting from the main path. The Goblin King quests are some of the more annoying tasks, and it's not enough to just complete one for his highness and move on.

There are five Goblin King quests in The Forge, each a little more difficult (and expensive) to complete than the last. It's a nice bit of XP, but the biggest incentive...