The volcano is a feature of the ancient city of the Ma'qwa Urqu.
In Campaign Mode, the volcano alone is no threat. Upon reaching Wave 5, a Savage Brute will emerge from the upper western hut, with a damsel in distress thrown over his shoulder. The brute will take a slow journey to the edge of the volcano, stopping along the way to pose. If he gets to the edge without being defeated, he'll throw the princess in and start off a chain of events.
The volcano will erupt sending balls of molten rock onto your troops dealing 100 damage in an area of effect. To prevent the volcano erupting, defeat the Brute before he gets there. Certain towers such as a Crossbow Fort can reach the Brute and kill him. The plateau and the wooden bridge are also accessible by any Hero, and Call Reinforcements or even a Rain of Fire can also be used to stop the Brute.