Complex sentence: In 41 BC, at Cleopatra's instigation, Mark Antony ordered Arsinoë's execution on the steps of the temple, a gross violation of the temple sanctuary and an act which scandalised Rome.
Split into simpler sentences: In 41 BC, at Cleopatra's instigation, Mark Antony ordered Arsinoë's execution on the steps of the temple. Her murder was a gross violation of the temple sanctuary and an act which scandalised Rome.