The Cove of Swords Deep

The Cove of Swords Deep is an adventure for characters level 4-6. The adventure begins on an island near the kingdom of Salete. Adventurers may have got there in different ways, that's up to the DM. Apparently an old feud between the tribes of the place has awakened an ancient evil hidden in a subterranean cove. Now it's up to the adventurers to resolve the situation.
Solve the thermoiel that plagues the island and its people.