Complex sentence: Prospero and his court are presented as indifferent to the sufferings of the population at large, intending to await the end of the plague in luxury and safety behind the walls of their secure refuge, having welded the doors shut.
Split into simpler sentences: Prospero and his court are indifferent to the sufferings of the population at large. They intend to await the end of the plague in luxury and safety behind the walls of their secure refuge, having welded the doors shut.