Complex sentence: The Manichæans did all they could to compel the inquisitor to cease from preaching against their errors and propaganda: persecutions, calumnies, threats, nothing was left untried.
Split into simpler sentences: The Manichæans did all they could to compel the inquisitor to cease from preaching against their errors and propaganda. Persecutions, calumnies, threats, nothing was left untried.