The Darkin mountain range was a massive place in the Darknar Region, spanning over 10,000 miles in length. The place contained tens of thousands of mountains and hills even though most of those hills and even some mountains were actually mountain golems in their almost constant state of rest.
With how sparse the mines and caves in this place were, the girls would find it difficult to map the entirety of the mountain range even with their maximum movement speed. Moreover, they would be unable to move freely in this place as even attracting the attention of a single mountain golem would set them back by a full day.
The golems were indeed the most troublesome monster to face in the Darknar region as their complete immunity to magic below the level of a demigod made them almost impossible to kill. They also had high physical resistance and various other insane resistances, making them the perfect tank monsters.