as a player of RTS,I can’t help but cringe. I use the tactic of a turtle merchant. to heck with rune crafting, earth manipulation. He could have closed off entrance to his valley all the way to the top of the mountains. allowing the time to purchase 100 farmers, 100 gatherers , 100 hunters, 100 scouts. then use the same method to make entracate caves in the mountains leaving the valley. next I would tunnel all over for hundreds of miles around the valley for surprise attacks and places to sleep during the day. next would be lava foundry,lots of them. replanting the forest that would be gone after a few weeks. the only goblin making babies would be the 4 armed worker,then make him a leader