Complex sentence: During the Decian persecution he was taken to Nicaea about the year 250 he was tortured and in a horrible manner and beheaded with a sword after he had converted the heathen prefect Licius.
Split into simpler sentences: During the Decian persecution he was taken to Nicaea about the year 250 and was tortured in a horrible manner. He was beheaded with a sword after he had converted the heathen prefect Licius.