Complex sentence: It is explained that the barrel contains a medicine for a plague on the planet Ornara, which is produced on the other planet, Brekka whose entire economy has become centered on producing and refining the drug.
Split into simpler sentences: It is explained that the barrel contains a medicine for a plague on the planet Ornara. The medicine is produced on the planet Brekka, whose entire economy has become centered on producing and refining the drug.