Complex sentence: Daniel is an official in the Persian empire under King Darius, who (at the instigation of his other officials) had made a decree that no-one was to offer prayer to any god or man except him for a period of thirty days.
Split into simpler sentences: Daniel is an official in the Persian empire under King Darius. Darius (at the instigation of his other officials) had made a decree that no-one was to offer prayer to any god or man except him for a period of thirty days.