Complex sentence: Located in the caldera of a dormant volcano, Cauldron is a medium-sized city founded by Surabar Spellmason around 500-600 years before the nominal "present day" in the campaign.
Split into simpler sentences: Located in the caldera of a dormant volcano, Cauldron is a medium-sized city. The city of Cauldron was founded by Surabar Spellmason around 500-600 years before the nominal "present day" in the campaign.