Complex sentence: The British brig "Comet" had fallen behind and now that the wind was gone she drifted away from the rest of the convoy and was attacked by 200 to 300 Greek pirates in five boats called mistikos.
Split into simpler sentences: The British brig "Comet" had fallen behind drifted away from the rest of the convoy. She was attacked by 200 to 300 Greek pirates in five boats called mistikos.